From 098c3ea6ef166eec332309c82f5e7469003d017a Mon Sep 17 00:00:00 2001 From: John Baldwin Date: Wed, 13 Oct 1999 01:45:20 +0000 Subject: [PATCH] Indent the programming-tools article. This is a whitespace-only commit, so translators can ignore this commit. PR: docs/14243 Submitted by: Neil Blakey-Milner --- .../articles/programming-tools/article.sgml | 3233 +++++++++-------- .../articles/programming-tools/article.sgml | 3233 +++++++++-------- 2 files changed, 3562 insertions(+), 2904 deletions(-) diff --git a/en_US.ISO8859-1/articles/programming-tools/article.sgml b/en_US.ISO8859-1/articles/programming-tools/article.sgml index 18badea392..d32b3869f8 100644 --- a/en_US.ISO8859-1/articles/programming-tools/article.sgml +++ b/en_US.ISO8859-1/articles/programming-tools/article.sgml @@ -1,560 +1,677 @@ - +
- - -A User's Guide to FreeBSD Programming Tools - - - -James -Raynard - -
-jraynard@FreeBSD.org -
- - - -August 17, 1997 - - -1997 -James Raynard - - -This document is an introduction to using some of the programming -tools supplied with FreeBSD, although much of it will be applicable to -many other versions of Unix. It does not attempt to describe -coding in any detail. Most of the document assumes little or no -previous programming knowledge, although it is hoped that most -programmers will find something of value in it - - - -Introduction<anchor id=foo> - -FreeBSD offers an excellent development environment. Compilers -for C, C++, and Fortran and an assembler come with the basic system, -not to mention a Perl interpreter and classic Unix tools such as -sed and awk. If that is not enough, there are -many more compilers and interpreters in the Ports collection. FreeBSD -is very compatible with standards such as POSIX and -ANSI C, as well with its own BSD heritage, so it is -possible to write applications that will compile and run with little -or no modification on a wide range of platforms. - -However, all this power can be rather overwhelming at first if -you've never written programs on a Unix platform before. This -document aims to help you get up and running, without getting too -deeply into more advanced topics. The intention is that this document -should give you enough of the basics to be able to make some sense of -the documentation. - -Most of the document requires little or no knowledge of -programming, although it does assume a basic competence with using -Unix and a willingness to learn! - - - - -Introduction to Programming - -A program is a set of instructions that tell the computer to do -various things; sometimes the instruction it has to perform depends -on what happened when it performed a previous instruction. This -section gives an overview of the two main ways in which you can give -these instructions, or commands as they are usually -called. One way uses an interpreter, the other a -compiler. As human languages are too difficult for a -computer to understand in an unambiguous way, commands are usually -written in one or other languages specially designed for the -purpose. - - - - -Interpreters - -With an interpreter, the language comes as an environment, where you -type in commands at a prompt and the environment executes them for -you. For more complicated programs, you can type the commands into a -file and get the interpreter to load the file and execute the commands -in it. If anything goes wrong, many interpreters will drop you into a -debugger to help you track down the problem. - -The advantage of this is that you can see the results of your -commands immediately, and mistakes can be corrected readily. The -biggest disadvantage comes when you want to share your programs with -someone. They must have the same interpreter, or you must have some -way of giving it to them, and they need to understand how to use it. -Also users may not appreciate being thrown into a debugger if they -press the wrong key! From a performance point of view, interpreters -can use up a lot of memory, and generally do not generate code as -efficiently as compilers. - -In my opinion, interpreted languages are the best way to start -if you have not done any programming before. This kind of environment -is typically found with languages like Lisp, Smalltalk, Perl and -Basic. It could also be argued that the Unix shell (sh, -csh) is itself an interpreter, and many people do in fact -write shell scripts to help with various -housekeeping tasks on their machine. Indeed, part of the -original Unix philosophy was to provide lots of small utility -programs that could be linked together in shell scripts to perform -useful tasks. - - - - -Interpreters available with FreeBSD - -Here is a list of interpreters that are available as FreeBSD -packages, with a brief discussion of some of the more popular -interpreted languages. - -To get one of these packages, all you need to do is to click on -the hotlink for the package, then run - -&prompt.root; pkg_add package name - -as root. Obviously, you will need to have a fully functional FreeBSD -2.1.0 or later system for the package to work! - - -BASIC - -Short for Beginner's All-purpose Symbolic Instruction -Code. Developed in the 1950s for teaching University students to -program and provided with every self-respecting personal computer in -the 1980s, BASIC has been the first programming language -for many programmers. It's also the foundation for Visual -Basic. - -The Bywater -Basic Interpreter and the Phil -Cockroft's Basic Interpreter (formerly Rabbit Basic) are -available as FreeBSD FreeBSD -packages - - - -Lisp -A language that was developed in the late 1950s as an alternative to -the number-crunching languages that were popular at the time. -Instead of being based on numbers, Lisp is based on lists; in fact -the name is short for List Processing. Very popular in AI -(Artificial Intelligence) circles. - -Lisp is an extremely powerful and sophisticated language, but -can be rather large and unwieldy. - -FreeBSD has GNU -Common Lisp available as a package. - - - - -Perl -Very popular with system administrators for writing -scripts; also often used on World Wide Web servers for writing CGI -scripts. - -Version 4, which is probably still the most widely-used -version, comes with FreeBSD; the newer Perl -Version 5 is available as a package. - - - - -Scheme -A dialect of Lisp that is rather more compact and -cleaner than Common Lisp. Popular in Universities as it is simple -enough to teach to undergraduates as a first language, while it has a -high enough level of abstraction to be used in research work. - -FreeBSD has packages of the -Elk Scheme Interpreter, the -MIT Scheme Interpreter and the -SCM Scheme Interpreter. - - - - -Icon -The Icon Programming Language. - - - -Logo -Brian Harvey's LOGO Interpreter. - - - -Python -The Python Object-Oriented Programming Language - - - - - - - - -Compilers - -Compilers are rather different. First of all, you write your -code in a file (or files) using an editor. You then run the compiler -and see if it accepts your program. If it did not compile, grit your -teeth and go back to the editor; if it did compile and gave you a -program, you can run it either at a shell command prompt or in a -debugger to see if it works properly.If you run it in -the shell, you may get a core dump. - -Obviously, this is not quite as direct as using an interpreter. -However it allows you to do a lot of things which are very difficult -or even impossible with an interpreter, such as writing code which -interacts closely with the operating system—or even writing -your own operating system! It's also useful if you need to write very -efficient code, as the compiler can take its time and optimise the -code, which would not be acceptable in an interpreter. And -distributing a program written for a compiler is usually more -straightforward than one written for an interpreter—you can just -give them a copy of the executable, assuming they have the same -operating system as you. - -Compiled languages include Pascal, C and C++. C and C++ are rather -unforgiving languages, and best suited to more experienced -programmers; Pascal, on the other hand, was designed as an educational -language, and is quite a good language to start with. Unfortunately, -FreeBSD doesn't have any Pascal support, except for a Pascal-to-C -converter in the ports. - -As the edit-compile-run-debug cycle is rather tedious when -using separate programs, many commercial compiler makers have -produced Integrated Development Environments (IDEs -for short). FreeBSD does not have an IDE as such; however -it is possible to use Emacs for this purpose. This is discussed in -. - - - - - -Compiling with <command>cc</command> - -This section deals only with the GNU compiler for C and C++, -since that comes with the base FreeBSD system. It can be invoked by -either cc or gcc. The details of producing a -program with an interpreter vary considerably between interpreters, -and are usually well covered in the documentation and on-line help -for the interpreter. - -Once you've written your masterpiece, the next step is to convert it -into something that will (hopefully!) run on FreeBSD. This usually -involves several steps, each of which is done by a separate -program. - - -Pre-process your source code to remove comments and do other -tricks like expanding macros in C. - - -Check the syntax of your code to see if you have obeyed the -rules of the language. If you have not, it will complain! - - -Convert the source code into assembly -language—this is very close to machine code, but still -understandable by humans. Allegedly.To be strictly -accurate, cc converts the source code into its own, -machine-independent p-code instead of assembly language -at this stage. - -Convert the assembly language into machine -code—yep, we are talking bits and bytes, ones and zeros -here. - -Check that you have used things like functions and global -variables in a consistent way. For example, if you have called a -non-existent function, it will complain. - -If you are trying to produce an executable from several -source code files, work out how to fit them all together. - -Work out how to produce something that the system's run-time -loader will be able to load into memory and run. - -Finally, write the executable on the file -system. - - - -The word compiling is often used to refer to just -steps 1 to 4—the others are referred to as -linking. Sometimes step 1 is referred to as -pre-processing and steps 3-4 as -assembling. - -Fortunately, almost all this detail is hidden from you, as -cc is a front end that manages calling all these programs -with the right arguments for you; simply typing - -&prompt.user; cc foobar.c - -will cause foobar.c to be compiled by all the -steps above. If you have more than one file to compile, just do -something like - -&prompt.user; cc foo.c bar.c - -Note that the syntax checking is just that—checking the -syntax. It will not check for any logical mistakes you may have made, -like putting the program into an infinite loop, or using a bubble -sort when you meant to use a binary sort.In case you -didn't know, a binary sort is an efficient way of sorting things into -order and a bubble sort isn't. - -There are lots and lots of options for cc, which -are all in the man page. Here are a few of the most important ones, -with examples of how to use them. - - - - -The output name of the file. If you do not use this -option, cc will produce an executable called -a.out.The reasons for this are buried in -the mists of history. - - -&prompt.user; cc foobar.c executable is a.out -&prompt.user; cc -o foobar foobar.c executable is foobar - - - - - -Just compile the file, do not link it. Useful for toy -programs where you just want to check the syntax, or if you are using -a Makefile. - - -&prompt.user; cc -c foobar.c - - -This will produce an object file (not an -executable) called foobar.o. This can be linked -together with other object files into an executable. - - - - - - -Create a debug version of the executable. This makes -the compiler put information into the executable about which line of -which source file corresponds to which function call. A debugger can -use this information to show the source code as you step through the -program, which is very useful; the disadvantage -is that all this extra information makes the program much bigger. -Normally, you compile with while you are -developing a program and then compile a release -version without when you're satisfied it -works properly. - - -&prompt.user; cc -g foobar.c - - -This will produce a debug version of the -program.Note, we didn't use the -flag to specify the executable name, so we will get an executable -called a.out. Producing a debug version called -foobar is left as an exercise for the -reader! - - - - - - -Create an optimised version of the executable. The -compiler performs various clever tricks to try and produce an -executable that runs faster than normal. You can add a number after -the to specify a higher level of optimisation, -but this often exposes bugs in the compiler's optimiser. For -instance, the version of cc that comes with the -2.1.0 release of FreeBSD is known to produce bad code with the - option in some circumstances. - -Optimisation is usually only turned on when compiling a release -version. - - -&prompt.user; cc -O -o foobar foobar.c - - -This will produce an optimised version of -foobar. - - - - - -The following three flags will force cc to -check that your code complies to the relevant international standard, -often referred to as the ANSI standard, though -strictly speaking it is an ISO standard. - - - - - -Enable all the warnings which the authors of -cc believe are worthwhile. Despite the name, it -will not enable all the warnings cc is capable -of. - - - - - - -Turn off most, but not all, of the non-ANSI C -features provided by cc. Despite the name, it does -not guarantee strictly that your code will comply to the -standard. - - - - - - - -Turn off all -cc's non-ANSI C features. - - - - - -Without these flags, cc will allow you to -use some of its non-standard extensions to the standard. Some of -these are very useful, but will not work with other compilers—in -fact, one of the main aims of the standard is to allow people to -write code that will work with any compiler on any system. This is -known as portable code. - -Generally, you should try to make your code as portable as -possible, as otherwise you may have to completely re-write the -program later to get it to work somewhere else—and who knows -what you may be using in a few years time? - - -&prompt.user; cc -Wall -ansi -pedantic -o foobar foobar.c - - -This will produce an executable foobar -after checking foobar.c for standard -compliance. - - - - - -Specify a function library to be used during when -linking. - -The most common example of this is when compiling a program that -uses some of the mathematical functions in C. Unlike most other -platforms, these are in a separate library from the standard C one -and you have to tell the compiler to add it. - -The rule is that if the library is called -libsomething.a, you -give cc the argument -. For example, -the math library is libm.a, so you give -cc the argument . A common -gotcha with the math library is that it has to be the -last library on the command line. - - -&prompt.user; cc -o foobar foobar.c -lm - - -This will link the math library functions into -foobar. - -If you are compiling C++ code, you need to add -, or if you are using -FreeBSD 2.2 or later, to the command line argument to link the C++ -library functions. Alternatively, you can run c++ -instead of cc, which does this for you. -c++ can also be invoked as g++ -on FreeBSD. - - -&prompt.user; cc -o foobar foobar.cc -lg++ For FreeBSD 2.1.6 and earlier + + A User's Guide to FreeBSD Programming Tools + + + + James + + Raynard + + +
+ jraynard@FreeBSD.org +
+ + + + + August 17, 1997 + + + 1997 + James Raynard + + + + This document is an introduction to using some of the + programming tools supplied with FreeBSD, although much of it + will be applicable to many other versions of Unix. It does + not attempt to describe coding in any + detail. Most of the document assumes little or no previous + programming knowledge, although it is hoped that most + programmers will find something of value in it + + + + + Introduction<anchor id=foo> + + FreeBSD offers an excellent development environment. + Compilers for C, C++, and Fortran and an assembler come with the + basic system, not to mention a Perl interpreter and classic Unix + tools such as sed and awk. If that is + not enough, there are many more compilers and interpreters in + the Ports collection. FreeBSD is very compatible with standards + such as POSIX and ANSI C, as well with + its own BSD heritage, so it is possible to write applications + that will compile and run with little or no modification on a + wide range of platforms. + + However, all this power can be rather overwhelming at first + if you've never written programs on a Unix platform before. + This document aims to help you get up and running, without + getting too deeply into more advanced topics. The intention is + that this document should give you enough of the basics to be + able to make some sense of the documentation. + + Most of the document requires little or no knowledge of + programming, although it does assume a basic competence with + using Unix and a willingness to learn! + + + + Introduction to Programming + + A program is a set of instructions that tell the computer to + do various things; sometimes the instruction it has to perform + depends on what happened when it performed a previous + instruction. This section gives an overview of the two main + ways in which you can give these instructions, or + commands as they are usually called. One way + uses an interpreter, the other a + compiler. As human languages are too difficult for + a computer to understand in an unambiguous way, commands are + usually written in one or other languages specially designed for + the purpose. + + + Interpreters + + With an interpreter, the language comes as an environment, + where you type in commands at a prompt and the environment + executes them for you. For more complicated programs, you can + type the commands into a file and get the interpreter to load + the file and execute the commands in it. If anything goes + wrong, many interpreters will drop you into a debugger to help + you track down the problem. + + The advantage of this is that you can see the results of + your commands immediately, and mistakes can be corrected + readily. The biggest disadvantage comes when you want to + share your programs with someone. They must have the same + interpreter, or you must have some way of giving it to them, + and they need to understand how to use it. Also users may not + appreciate being thrown into a debugger if they press the + wrong key! From a performance point of view, interpreters can + use up a lot of memory, and generally do not generate code as + efficiently as compilers. + + In my opinion, interpreted languages are the best way to + start if you have not done any programming before. This kind + of environment is typically found with languages like Lisp, + Smalltalk, Perl and Basic. It could also be argued that the + Unix shell (sh, csh) is itself an + interpreter, and many people do in fact write shell + scripts to help with various + housekeeping tasks on their machine. Indeed, part + of the original Unix philosophy was to provide lots of small + utility programs that could be linked together in shell + scripts to perform useful tasks. + + + + Interpreters available with FreeBSD + + Here is a list of interpreters that are available as + FreeBSD + packages, with a brief discussion of some of the + more popular interpreted languages. + + To get one of these packages, all you need to do is to + click on the hotlink for the package, then run + + &prompt.root; pkg_add package name + + + as root. Obviously, you will need to have a fully + functional FreeBSD 2.1.0 or later system for the package to + work! + + + + BASIC + + + Short for Beginner's All-purpose Symbolic + Instruction Code. Developed in the 1950s for teaching + University students to program and provided with every + self-respecting personal computer in the 1980s, + BASIC has been the first programming + language for many programmers. It's also the foundation + for Visual Basic. + + The Bywater + Basic Interpreter and the Phil + Cockroft's Basic Interpreter (formerly Rabbit + Basic) are available as FreeBSD FreeBSD + packages + + + + + Lisp + + + A language that was developed in the late 1950s as + an alternative to the number-crunching + languages that were popular at the time. Instead of + being based on numbers, Lisp is based on lists; in fact + the name is short for List Processing. + Very popular in AI (Artificial Intelligence) + circles. + + Lisp is an extremely powerful and sophisticated + language, but can be rather large and unwieldy. + + FreeBSD has GNU + Common Lisp available as a package. + + + + + Perl + + + Very popular with system administrators for writing + scripts; also often used on World Wide Web servers for + writing CGI scripts. + + Version 4, which is probably still the most + widely-used version, comes with FreeBSD; the newer + Perl + Version 5 is available as a package. + + + + + Scheme + + + A dialect of Lisp that is rather more compact and + cleaner than Common Lisp. Popular in Universities as it + is simple enough to teach to undergraduates as a first + language, while it has a high enough level of + abstraction to be used in research work. + + FreeBSD has packages of the Elk + Scheme Interpreter, the MIT + Scheme Interpreter and the SCM + Scheme Interpreter. + + + + + Icon + + + The + Icon Programming Language. + + + + + Logo + + + Brian + Harvey's LOGO Interpreter. + + + + + Python + + + The + Python Object-Oriented Programming + Language + + + + + + + Compilers + + Compilers are rather different. First of all, you write + your code in a file (or files) using an editor. You then run + the compiler and see if it accepts your program. If it did + not compile, grit your teeth and go back to the editor; if it + did compile and gave you a program, you can run it either at a + shell command prompt or in a debugger to see if it works + properly. + + + If you run it in the shell, you may get a core + dump. + + + Obviously, this is not quite as direct as using an + interpreter. However it allows you to do a lot of things + which are very difficult or even impossible with an + interpreter, such as writing code which interacts closely with + the operating system—or even writing your own operating + system! It's also useful if you need to write very efficient + code, as the compiler can take its time and optimise the code, + which would not be acceptable in an interpreter. And + distributing a program written for a compiler is usually more + straightforward than one written for an interpreter—you + can just give them a copy of the executable, assuming they + have the same operating system as you. + + Compiled languages include Pascal, C and C++. C and C++ + are rather unforgiving languages, and best suited to more + experienced programmers; Pascal, on the other hand, was + designed as an educational language, and is quite a good + language to start with. Unfortunately, FreeBSD doesn't have + any Pascal support, except for a Pascal-to-C converter in the + ports. + + As the edit-compile-run-debug cycle is rather tedious when + using separate programs, many commercial compiler makers have + produced Integrated Development Environments + (IDEs for short). FreeBSD does not have an + IDE as such; however it is possible to use Emacs + for this purpose. This is discussed in . + + + + + Compiling with <command>cc</command> + + This section deals only with the GNU compiler for C and C++, + since that comes with the base FreeBSD system. It can be + invoked by either cc or gcc. The + details of producing a program with an interpreter vary + considerably between interpreters, and are usually well covered + in the documentation and on-line help for the + interpreter. + + Once you've written your masterpiece, the next step is to + convert it into something that will (hopefully!) run on FreeBSD. + This usually involves several steps, each of which is done by a + separate program. + + + + Pre-process your source code to remove comments and do + other tricks like expanding macros in C. + + + + Check the syntax of your code to see if you have obeyed + the rules of the language. If you have not, it will + complain! + + + + Convert the source code into assembly + language—this is very close to machine code, but still + understandable by humans. Allegedly. + + + To be strictly accurate, cc converts the + source code into its own, machine-independent + p-code instead of assembly language at + this stage. + + + + + Convert the assembly language into machine + code—yep, we are talking bits and bytes, ones and + zeros here. + + + + Check that you have used things like functions and + global variables in a consistent way. For example, if you + have called a non-existent function, it will + complain. + + + + If you are trying to produce an executable from several + source code files, work out how to fit them all + together. + + + + Work out how to produce something that the system's + run-time loader will be able to load into memory and + run. + + + + Finally, write the executable on the file system. + + + + The word compiling is often used to refer to + just steps 1 to 4—the others are referred to as + linking. Sometimes step 1 is referred to as + pre-processing and steps 3-4 as + assembling. + + Fortunately, almost all this detail is hidden from you, as + cc is a front end that manages calling all these + programs with the right arguments for you; simply typing + + &prompt.user; cc foobar.c + + + will cause foobar.c to be compiled by all the + steps above. If you have more than one file to compile, just do + something like + + &prompt.user; cc foo.c bar.c + + + Note that the syntax checking is just that—checking + the syntax. It will not check for any logical mistakes you may + have made, like putting the program into an infinite loop, or + using a bubble sort when you meant to use a binary + sort. + + + In case you didn't know, a binary sort is an efficient + way of sorting things into order and a bubble sort + isn't. + + + There are lots and lots of options for cc, which + are all in the man page. Here are a few of the most important + ones, with examples of how to use them. + + + + + + + The output name of the file. If you do not use this + option, cc will produce an executable called + a.out. + + + The reasons for this are buried in the mists of + history. + + + + &prompt.user; cc foobar.c executable is a.out +&prompt.user; cc -o foobar foobar.c executable is foobar + + + + + + + + + + Just compile the file, do not link it. Useful for toy + programs where you just want to check the syntax, or if + you are using a Makefile. + + + &prompt.user; cc -c foobar.c + + + + This will produce an object file (not an + executable) called foobar.o. This + can be linked together with other object files into an + executable. + + + + + + + + Create a debug version of the executable. This makes + the compiler put information into the executable about + which line of which source file corresponds to which + function call. A debugger can use this information to show + the source code as you step through the program, which is + very useful; the disadvantage is that + all this extra information makes the program much bigger. + Normally, you compile with while you + are developing a program and then compile a release + version without when you're + satisfied it works properly. + + + &prompt.user; cc -g foobar.c + + + + This will produce a debug version of the + program. + + + Note, we didn't use the flag + to specify the executable name, so we will get an + executable called a.out. + Producing a debug version called + foobar is left as an exercise for + the reader! + + + + + + + + + Create an optimised version of the executable. The + compiler performs various clever tricks to try and produce + an executable that runs faster than normal. You can add a + number after the to specify a higher + level of optimisation, but this often exposes bugs in the + compiler's optimiser. For instance, the version of + cc that comes with the 2.1.0 release of + FreeBSD is known to produce bad code with the + option in some circumstances. + + Optimisation is usually only turned on when compiling + a release version. + + + &prompt.user; cc -O -o foobar foobar.c + + + + This will produce an optimised version of + foobar. + + + + + The following three flags will force cc + to check that your code complies to the relevant international + standard, often referred to as the ANSI + standard, though strictly speaking it is an + ISO standard. + + + + + + + Enable all the warnings which the authors of + cc believe are worthwhile. Despite the + name, it will not enable all the warnings + cc is capable of. + + + + + + + + Turn off most, but not all, of the + non-ANSI C features provided by + cc. Despite the name, it does not + guarantee strictly that your code will comply to the + standard. + + + + + + + + Turn off all + cc's non-ANSI C + features. + + + + + Without these flags, cc will allow you to + use some of its non-standard extensions to the standard. Some + of these are very useful, but will not work with other + compilers—in fact, one of the main aims of the standard is + to allow people to write code that will work with any compiler + on any system. This is known as portable + code. + + Generally, you should try to make your code as portable as + possible, as otherwise you may have to completely re-write the + program later to get it to work somewhere else—and who + knows what you may be using in a few years time? + + + &prompt.user; cc -Wall -ansi -pedantic -o foobar foobar.c + + + + This will produce an executable foobar + after checking foobar.c for standard + compliance. + + + + + + + Specify a function library to be used during when + linking. + + The most common example of this is when compiling a + program that uses some of the mathematical functions in C. + Unlike most other platforms, these are in a separate + library from the standard C one and you have to tell the + compiler to add it. + + The rule is that if the library is called + libsomething.a, + you give cc the argument + . + For example, the math library is + libm.a, so you give + cc the argument . + A common gotcha with the math library is + that it has to be the last library on the command + line. + + + &prompt.user; cc -o foobar foobar.c -lm + + + + This will link the math library functions into + foobar. + + If you are compiling C++ code, you need to add + , or if + you are using FreeBSD 2.2 or later, to the command line + argument to link the C++ library functions. + Alternatively, you can run c++ instead + of cc, which does this for you. + c++ can also be invoked as + g++ on FreeBSD. + + + &prompt.user; cc -o foobar foobar.cc -lg++ For FreeBSD 2.1.6 and earlier &prompt.user; cc -o foobar foobar.cc -lstdc++ For FreeBSD 2.2 and later -&prompt.user; c++ -o foobar foobar.cc - +&prompt.user; c++ -o foobar foobar.cc + + -Each of these will both produce an executable -foobar from the C++ source file -foobar.cc. Note that, on Unix systems, C++ -source files traditionally end in .C, -.cxx or .cc, rather than -the MS-DOS style .cpp -(which was already used for something else). gcc -used to rely on this to work out what kind of compiler to use on the -source file; however, this restriction no longer applies, so you may -now call your C++ files .cpp with -impunity! + Each of these will both produce an executable + foobar from the C++ source file + foobar.cc. Note that, on Unix + systems, C++ source files traditionally end in + .C, .cxx or + .cc, rather than the + MS-DOS style + .cpp (which was already used for + something else). gcc used to rely on + this to work out what kind of compiler to use on the + source file; however, this restriction no longer applies, + so you may now call your C++ files + .cpp with impunity! + + + - - - - - -Common <command>cc</command> Queries and Problems + + Common <command>cc</command> Queries and Problems - - - -I am trying to write a program which uses the -sin() function and I get an error like this. -What does it mean? - - -/var/tmp/cc0143941.o: Undefined symbol `_sin' referenced from text segment - - - -When using mathematical functions like -sin(), you have to tell cc to -link in the math library, like so: - -&prompt.user; cc -o foobar foobar.c -lm - - - - - -All right, I wrote this simple program to practice using -. All it does is raise 2.1 to the power of 6. - - -#include <stdio.h> + + + + I am trying to write a program which uses the + sin() function and I get an error + like this. What does it mean? + + + /var/tmp/cc0143941.o: Undefined symbol `_sin' referenced from text segment + + + + + + When using mathematical functions like + sin(), you have to tell + cc to link in the math library, like + so: + + + &prompt.user; cc -o foobar foobar.c -lm + + + + + + + + All right, I wrote this simple program to practice + using . All it does is raise 2.1 to + the power of 6. + + + #include <stdio.h> int main() { float f; @@ -562,588 +679,707 @@ int main() { f = pow(2.1, 6); printf("2.1 ^ 6 = %f\n", f); return 0; -} - - -and I compiled it as: - - -&prompt.user; cc temp.c -lm - - -like you said I should, but I get this when I run it: - - -&prompt.user; ./a.out -2.1 ^ 6 = 1023.000000 - - -This is not the right answer! What is -going on? - - -When the compiler sees you call a function, it checks if it -has already seen a prototype for it. If it has not, it assumes the -function returns an int, which is -definitely not what you want here. - - - - -So how do I fix this? - - -The prototypes for the mathematical functions are in -math.h. If you include this file, the compiler -will be able to find the prototype and it will stop doing strange -things to your calculation! - - -#include <math.h> +} + + + + and I compiled it as: + + + &prompt.user; cc temp.c -lm + + + + like you said I should, but I get this when I run + it: + + + &prompt.user; ./a.out +2.1 ^ 6 = 1023.000000 + + + + This is not the right answer! + What is going on? + + + + When the compiler sees you call a function, it + checks if it has already seen a prototype for it. If it + has not, it assumes the function returns an + int, which is definitely not what you want + here. + + + + + + So how do I fix this? + + + + The prototypes for the mathematical functions are in + math.h. If you include this file, + the compiler will be able to find the prototype and it + will stop doing strange things to your + calculation! + + + #include <math.h> #include <stdio.h> int main() { -... - - -After recompiling it as you did before, run it: - - -&prompt.user; ./a.out -2.1 ^ 6 = 85.766121 - - -If you are using any of the mathematical functions, -always include math.h and -remember to link in the math library. - - - - -I compiled a file called foobar.c and I -cannot find an executable called foobar. Where's -it gone? - - -Remember, cc will call the executable -a.out unless you tell it differently. Use the - option: - - -&prompt.user; cc -o foobar foobar.c - - - - - -OK, I have an executable called foobar, -I can see it when I run ls, but when I type in -foobar at the command prompt it tells me there is -no such file. Why can it not find it? - - -Unlike MS-DOS, Unix does not look in the -current directory when it is trying to find out which executable you -want it to run, unless you tell it to. Either type -./foobar, which means run the file called -foobar in the current directory, or -change your PATH -environment variable so that it looks something like - - -bin:/usr/bin:/usr/local/bin:. - - -The dot at the end means look in the current directory if it is not in -any of the others. - - - - -I called my executable test, but -nothing happens when I run it. What is going on? - - -Most Unix systems have a program called -test in /usr/bin and the -shell is picking that one up before it gets to checking the current -directory. Either type: - - -&prompt.user; ./test - - -or choose a better name for your program! - - - - -I compiled my program and it seemed to run all right at -first, then there was an error and it said something about core -dumped. What does that mean? - - -The name core dump dates back to the -very early days of Unix, when the machines used core memory for -storing data. Basically, if the program failed under certain -conditions, the system would write the contents of core memory to -disk in a file called core, which the programmer -could then pore over to find out what went wrong. - - - - -Fascinating stuff, but what I am supposed to do now? - - -Use gdb to analyse the core (see ). - - - - -When my program dumped core, it said something about a -segmentation fault. What's that? - - -This basically means that your program tried to perform some sort -of illegal operation on memory; Unix is designed to protect the -operating system and other programs from rogue programs. - -Common causes for this are: - - -Trying to write to a NULL pointer, eg - -char *foo = NULL; -strcpy(foo, "bang!"); - +... + + -Using a pointer that hasn't been initialised, eg - -char *foo; -strcpy(foo, "bang!"); - -The pointer will have some random value that, with luck, -will point into an area of memory that isn't available to -your program and the kernel will kill your program before -it can do any damage. If you're unlucky, it'll point -somewhere inside your own program and corrupt one of your -data structures, causing the program to fail -mysteriously. + After recompiling it as you did before, run + it: -Trying to access past the end of an array, eg - -int bar[20]; -bar[27] = 6; + + &prompt.user; ./a.out +2.1 ^ 6 = 85.766121 + + - Trying to store something in read-only memory, eg - -char *foo = "My string"; -strcpy(foo, "bang!"); - -Unix compilers often put string literals like -"My string" into -read-only areas of memory. + If you are using any of the mathematical functions, + always include + math.h and remember to link in the + math library. + + -Doing naughty things with -malloc() and free(), eg - -char bar[80]; -free(bar); - -or - -char *foo = malloc(27); + + + I compiled a file called + foobar.c and I cannot find an + executable called foobar. Where's + it gone? + + + + Remember, cc will call the + executable a.out unless you tell it + differently. Use the + + option: + + + &prompt.user; cc -o foobar foobar.c + + + + + + + + OK, I have an executable called + foobar, I can see it when I run + ls, but when I type in + foobar at the command prompt it tells + me there is no such file. Why can it not find + it? + + + + Unlike MS-DOS, Unix does not + look in the current directory when it is trying to find + out which executable you want it to run, unless you tell + it to. Either type ./foobar, which + means run the file called + foobar in the current + directory, or change your PATH environment + variable so that it looks something like + + + bin:/usr/bin:/usr/local/bin:. + + + + The dot at the end means look in the current + directory if it is not in any of the + others. + + + + + + I called my executable test, + but nothing happens when I run it. What is going + on? + + + + Most Unix systems have a program called + test in /usr/bin + and the shell is picking that one up before it gets to + checking the current directory. Either type: + + + &prompt.user; ./test + + + + or choose a better name for your program! + + + + + + I compiled my program and it seemed to run all right + at first, then there was an error and it said something + about core dumped. What does that + mean? + + + + The name core dump dates back + to the very early days of Unix, when the machines used + core memory for storing data. Basically, if the program + failed under certain conditions, the system would write + the contents of core memory to disk in a file called + core, which the programmer could + then pore over to find out what went wrong. + + + + + + Fascinating stuff, but what I am supposed to do + now? + + + + Use gdb to analyse the core (see + ). + + + + + + When my program dumped core, it said something about + a segmentation fault. What's + that? + + + + This basically means that your program tried to + perform some sort of illegal operation on memory; Unix + is designed to protect the operating system and other + programs from rogue programs. + + Common causes for this are: + + + + Trying to write to a NULL + pointer, eg + + char *foo = NULL; +strcpy(foo, "bang!"); + + + + + Using a pointer that hasn't been initialised, + eg + + char *foo; +strcpy(foo, "bang!"); + + + The pointer will have some random value that, + with luck, will point into an area of memory that + isn't available to your program and the kernel will + kill your program before it can do any damage. If + you're unlucky, it'll point somewhere inside your + own program and corrupt one of your data structures, + causing the program to fail mysteriously. + + + + Trying to access past the end of an array, + eg + + int bar[20]; +bar[27] = 6; + + + + + Trying to store something in read-only memory, + eg + + char *foo = "My string"; +strcpy(foo, "bang!"); + + + Unix compilers often put string literals like + "My string" into read-only areas + of memory. + + + + Doing naughty things with + malloc() and + free(), eg + + char bar[80]; +free(bar); + + + or + + char *foo = malloc(27); free(foo); -free(foo); - +free(foo); + + + - + Making one of these mistakes will not always lead to + an error, but they are always bad practice. Some + systems and compilers are more tolerant than others, + which is why programs that ran well on one system can + crash when you try them on an another. + + -Making one of these mistakes will not always lead to an -error, but they are always bad practice. Some systems and -compilers are more tolerant than others, which is why programs -that ran well on one system can crash when you try them on an -another. - - - - -Sometimes when I get a core dump it says bus -error. It says in my Unix book that this means a hardware -problem, but the computer still seems to be working. Is this -true? - - -No, fortunately not (unless of course you really do have a hardware -problem…). This is usually another way of saying that you -accessed memory in a way you shouldn't have. - - - - -This dumping core business sounds as though it could be quite -useful, if I can make it happen when I want to. Can I do this, or -do I have to wait until there's an error? - - -Yes, just go to another console or xterm, do -&prompt.user; ps - -to find out the process ID of your program, and do - -&prompt.user; kill -ABRT pid - -where pid is the -process ID you looked up. - -This is useful if your program has got stuck in an infinite -loop, for instance. If your program happens to trap -SIGABRT, there are several other signals which have -a similar effect. - - - + + + Sometimes when I get a core dump it says + bus error. It says in my Unix + book that this means a hardware problem, but the + computer still seems to be working. Is this + true? + - - + + No, fortunately not (unless of course you really do + have a hardware problem…). This is usually + another way of saying that you accessed memory in a way + you shouldn't have. + + + + + This dumping core business sounds as though it could + be quite useful, if I can make it happen when I want to. + Can I do this, or do I have to wait until there's an + error? + - -Make + + Yes, just go to another console or xterm, do - -What is <command>make</command>? + &prompt.user; ps + -When you're working on a simple program with only one or two source -files, typing in - -&prompt.user; cc file1.c file2.c - -is not too bad, but it quickly becomes very tedious when there are -several files—and it can take a while to compile, too. - -One way to get around this is to use object files and only recompile -the source file if the source code has changed. So we could have -something like: - -&prompt.user; cc file1.o file2.o … file37.c &hellip - -if we'd changed file37.c, but not any of the -others, since the last time we compiled. This may speed up the -compilation quite a bit, but doesn't solve the typing -problem. + to find out the process ID of your program, and + do -Or we could write a shell script to solve the typing problem, but it -would have to re-compile everything, making it very inefficient on a -large project. - -What happens if we have hundreds of source files lying about? What if -we're working in a team with other people who forget to tell us when -they've changed one of their source files that we use? - -Perhaps we could put the two solutions together and write something -like a shell script that would contain some kind of magic rule saying -when a source file needs compiling. Now all we need now is a program -that can understand these rules, as it's a bit too complicated for the -shell. - -This program is called make. It reads in a -file, called a makefile, that tells it how -different files depend on each other, and works out which files need -to be re-compiled and which ones don't. For example, a rule could say -something like if fromboz.o is older than -fromboz.c, that means someone must have changed -fromboz.c, so it needs to be -re-compiled. The makefile also has rules telling make -how to re-compile the source file, making it a -much more powerful tool. + &prompt.user; kill -ABRT pid + -Makefiles are typically kept in the same directory as the -source they apply to, and can be called -makefile, Makefile or -MAKEFILE. Most programmers use the name -Makefile, as this puts it near the top of a -directory listing, where it can easily be seen.They -don't use the MAKEFILE form as block capitals -are often used for documentation files like -README. - - + where + pid is + the process ID you looked up. - -Example of using <command>make</command> + This is useful if your program has got stuck in an + infinite loop, for instance. If your program happens to + trap SIGABRT, there are several other + signals which have a similar effect. + + + + + -Here's a very simple make file: - -foo: foo.c - cc -o foo foo.c - -It consists of two lines, a dependency line and a creation line. - -The dependency line here consists of the name of the program -(known as the target), followed by a colon, -then whitespace, then the name of the source file. When -make reads this line, it looks to see if -foo exists; if it exists, it compares the time -foo was last modified to the time -foo.c was last modified. If -foo does not exist, or is older than -foo.c, it then looks at the creation line to -find out what to do. In other words, this is the rule for working out -when foo.c needs to be re-compiled. + + Make -The creation line starts with a tab (press the -tab key) and then the command you would type to -create foo if you were doing it at a command -prompt. If foo is out of date, or does not -exist, make then executes this command to create -it. In other words, this is the rule which tells make how to -re-compile foo.c. + + What is <command>make</command>? -So, when you type make, it will make -sure that foo is up to date with respect to your -latest changes to foo.c. This principle can be -extended to Makefiles with hundreds of -targets—in fact, on FreeBSD, it is possible to compile the -entire operating system just by typing make -world in the appropriate directory! + When you're working on a simple program with only one or + two source files, typing in -Another useful property of makefiles is that the targets don't have -to be programs. For instance, we could have a make file that looks -like this: - -foo: foo.c + &prompt.user; cc file1.c file2.c + + + is not too bad, but it quickly becomes very tedious when + there are several files—and it can take a while to + compile, too. + + One way to get around this is to use object files and only + recompile the source file if the source code has changed. So + we could have something like: + + &prompt.user; cc file1.o file2.o … file37.c &hellip + + + if we'd changed file37.c, but not any + of the others, since the last time we compiled. This may + speed up the compilation quite a bit, but doesn't solve the + typing problem. + + Or we could write a shell script to solve the typing + problem, but it would have to re-compile everything, making it + very inefficient on a large project. + + What happens if we have hundreds of source files lying + about? What if we're working in a team with other people who + forget to tell us when they've changed one of their source + files that we use? + + Perhaps we could put the two solutions together and write + something like a shell script that would contain some kind of + magic rule saying when a source file needs compiling. Now all + we need now is a program that can understand these rules, as + it's a bit too complicated for the shell. + + This program is called make. It reads + in a file, called a makefile, that + tells it how different files depend on each other, and works + out which files need to be re-compiled and which ones don't. + For example, a rule could say something like if + fromboz.o is older than + fromboz.c, that means someone must have + changed fromboz.c, so it needs to be + re-compiled. The makefile also has rules telling + make how to re-compile the source file, + making it a much more powerful tool. + + Makefiles are typically kept in the same directory as the + source they apply to, and can be called + makefile, Makefile + or MAKEFILE. Most programmers use the + name Makefile, as this puts it near the + top of a directory listing, where it can easily be + seen. + + + They don't use the MAKEFILE form + as block capitals are often used for documentation files + like README. + + + + + Example of using <command>make</command> + + Here's a very simple make file: + + foo: foo.c + cc -o foo foo.c + + + It consists of two lines, a dependency line and a creation + line. + + The dependency line here consists of the name of the + program (known as the target), followed + by a colon, then whitespace, then the name of the source file. + When make reads this line, it looks to see + if foo exists; if it exists, it compares + the time foo was last modified to the + time foo.c was last modified. If + foo does not exist, or is older than + foo.c, it then looks at the creation line + to find out what to do. In other words, this is the rule for + working out when foo.c needs to be + re-compiled. + + The creation line starts with a tab (press + the tab key) and then the command you would + type to create foo if you were doing it + at a command prompt. If foo is out of + date, or does not exist, make then executes + this command to create it. In other words, this is the rule + which tells make how to re-compile + foo.c. + + So, when you type make, it will + make sure that foo is up to date with + respect to your latest changes to foo.c. + This principle can be extended to + Makefiles with hundreds of + targets—in fact, on FreeBSD, it is possible to compile + the entire operating system just by typing make + world in the appropriate directory! + + Another useful property of makefiles is that the targets + don't have to be programs. For instance, we could have a make + file that looks like this: + + foo: foo.c cc -o foo foo.c install: - cp foo /home/me - -We can tell make which target we want to make by typing: - -&prompt.user; make target - -make will then only look at that target and ignore any -others. For example, if we type make foo with the -makefile above, make will ignore the install target. - -If we just type make on its own, make -will always look at the first target and then stop without looking at -any others. So if we typed make here, it will -just go to the foo target, re-compile -foo if necessary, and then stop without going on -to the install target. + cp foo /home/me + -Notice that the install target doesn't -actually depend on anything! This means that the command on the -following line is always executed when we try to make that target by -typing make install. In this case, it will -copy foo into the user's home directory. This is -often used by application makefiles, so that the application can be -installed in the correct directory when it has been correctly -compiled. + We can tell make which target we want to make by + typing: -This is a slightly confusing subject to try and explain. If you -don't quite understand how make works, the best -thing to do is to write a simple program like hello -world and a make file like the one above and experiment. Then -progress to using more than one source file, or having the source -file include a header file. The touch command is -very useful here—it changes the date on a file without you -having to edit it. - - + &prompt.user; make target + - -FreeBSD Makefiles + make will then only look at that target + and ignore any others. For example, if we type + make foo with the makefile above, make + will ignore the install target. -Makefiles can be rather complicated to write. Fortunately, -BSD-based systems like FreeBSD come with some very powerful ones as -part of the system. One very good example of this is the FreeBSD -ports system. Here's the essential part of a typical ports -Makefile: -MASTER_SITES= ftp://freefall.cdrom.com/pub/FreeBSD/LOCAL_PORTS/ + If we just type make on its own, + make will always look at the first target and then stop + without looking at any others. So if we typed + make here, it will just go to the + foo target, re-compile + foo if necessary, and then stop without + going on to the install target. + + Notice that the install target doesn't + actually depend on anything! This means that the command on + the following line is always executed when we try to make that + target by typing make install. In this + case, it will copy foo into the user's + home directory. This is often used by application makefiles, + so that the application can be installed in the correct + directory when it has been correctly compiled. + + This is a slightly confusing subject to try and explain. + If you don't quite understand how make + works, the best thing to do is to write a simple program like + hello world and a make file like the one above + and experiment. Then progress to using more than one source + file, or having the source file include a header file. The + touch command is very useful here—it + changes the date on a file without you having to edit + it. + + + + FreeBSD Makefiles + + Makefiles can be rather complicated to write. Fortunately, + BSD-based systems like FreeBSD come with some very powerful + ones as part of the system. One very good example of this is + the FreeBSD ports system. Here's the essential part of a + typical ports Makefile: + + MASTER_SITES= ftp://freefall.cdrom.com/pub/FreeBSD/LOCAL_PORTS/ DISTFILES= scheme-microcode+dist-7.3-freebsd.tgz -.include <bsd.port.mk> - -Now, if we go to the directory for this port and type -make, the following happens: +.include <bsd.port.mk> + - -A check is made to see if the source code for this port is -already on the system. + Now, if we go to the directory for this port and type + make, the following happens: -If it isn't, an FTP connection to the URL in -MASTER_SITES is set up to download the -source. + + + A check is made to see if the source code for this + port is already on the system. + -The checksum for the source is calculated and compared it with -one for a known, good, copy of the source. This is to make sure that -the source was not corrupted while in transit. + + If it isn't, an FTP connection to the URL in + MASTER_SITES is set up to download the + source. + -Any changes required to make the source work on FreeBSD are -applied—this is known as patching. + + The checksum for the source is calculated and compared + it with one for a known, good, copy of the source. This + is to make sure that the source was not corrupted while in + transit. + -Any special configuration needed for the source is done. -(Many Unix program distributions try to work out which version of -Unix they are being compiled on and which optional Unix features are -present—this is where they are given the information in the -FreeBSD ports scenario). + + Any changes required to make the source work on + FreeBSD are applied—this is known as + patching. + -The source code for the program is compiled. In effect, -we change to the directory where the source was unpacked and do -make—the program's own make file has the -necessary information to build the program. + + Any special configuration needed for the source is + done. (Many Unix program distributions try to work out + which version of Unix they are being compiled on and which + optional Unix features are present—this is where + they are given the information in the FreeBSD ports + scenario). + -We now have a compiled version of the program. If we -wish, we can test it now; when we feel confident about the program, -we can type make install. This will cause the -program and any supporting files it needs to be copied into the -correct location; an entry is also made into a package -database, so that the port can easily be uninstalled later -if we change our mind about it. + + The source code for the program is compiled. In + effect, we change to the directory where the source was + unpacked and do make—the + program's own make file has the necessary information to + build the program. + - - -Now I think you'll agree that's rather impressive for a four -line script! + + We now have a compiled version of the program. If we + wish, we can test it now; when we feel confident about the + program, we can type make install. + This will cause the program and any supporting files it + needs to be copied into the correct location; an entry is + also made into a package database, so + that the port can easily be uninstalled later if we change + our mind about it. + + -The secret lies in the last line, which tells -make to look in the system makefile called -bsd.port.mk. It's easy to overlook this line, -but this is where all the clever stuff comes from—someone has -written a makefile that tells make to do all the -things above (plus a couple of other things I didn't mention, -including handling any errors that may occur) and anyone can get -access to that just by putting a single line in their own make -file! + Now I think you'll agree that's rather impressive for a + four line script! -If you want to have a look at these system makefiles, they're -in /usr/share/mk, but it's probably best to wait -until you've had a bit of practice with makefiles, as they are very -complicated (and if you do look at them, make sure you have a flask -of strong coffee handy!) + The secret lies in the last line, which tells + make to look in the system makefile called + bsd.port.mk. It's easy to overlook this + line, but this is where all the clever stuff comes + from—someone has written a makefile that tells + make to do all the things above (plus a + couple of other things I didn't mention, including handling + any errors that may occur) and anyone can get access to that + just by putting a single line in their own make file! - + If you want to have a look at these system makefiles, + they're in /usr/share/mk, but it's + probably best to wait until you've had a bit of practice with + makefiles, as they are very complicated (and if you do look at + them, make sure you have a flask of strong coffee + handy!) + - -More advanced uses of <command>make</command> + + More advanced uses of <command>make</command> -Make is a very powerful tool, and can do much -more than the simple example above shows. Unfortunately, there are -several different versions of make, and they all -differ considerably. The best way to learn what they can do is -probably to read the documentation—hopefully this introduction will -have given you a base from which you can do this. + Make is a very powerful tool, and can + do much more than the simple example above shows. + Unfortunately, there are several different versions of + make, and they all differ considerably. + The best way to learn what they can do is probably to read the + documentation—hopefully this introduction will have + given you a base from which you can do this. -The version of make that comes with FreeBSD is the Berkeley -make; there is a tutorial for it in -/usr/share/doc/psd/12.make. To view it, do - -&prompt.user; zmore paper.ascii.gz - -in that directory. - -Many applications in the ports use GNU -make, which has a very good set of info -pages. If you have installed any of these ports, GNU -make will automatically have been installed as -gmake. It's also available as a port and package -in its own right. + The version of make that comes with FreeBSD is the + Berkeley make; there is a tutorial + for it in /usr/share/doc/psd/12.make. To + view it, do -To view the info pages for GNU make, -you will have to edit the dir file in the -/usr/local/info directory to add an entry for -it. This involves adding a line like - - * Make: (make). The GNU Make utility. - -to the file. Once you have done this, you can type -info and then select -make from the menu (or in -Emacs, do C-h -i). + &prompt.user; zmore paper.ascii.gz + - - + in that directory. - -Debugging + Many applications in the ports use GNU + make, which has a very good set of + info pages. If you have installed any of these + ports, GNU make will automatically + have been installed as gmake. It's also + available as a port and package in its own right. - -The Debugger + To view the info pages for GNU + make, you will have to edit the + dir file in the + /usr/local/info directory to add an entry + for it. This involves adding a line like -The debugger that comes with FreeBSD is called -gdb (GNU -debugger). You start it up by typing - -&prompt.user; gdb progname - -although most people prefer to run it inside -Emacs. You can do this by: - -M-x gdb RET progname RET - -Using a debugger allows you to run the program under more -controlled circumstances. Typically, you can step through the program -a line at a time, inspect the value of variables, change them, tell -the debugger to run up to a certain point and then stop, and so on. -You can even attach to a program that's already running, or load a -core file to investigate why the program crashed. It's even possible -to debug the kernel, though that's a little trickier than the user -applications we'll be discussing in this section. + * Make: (make). The GNU Make utility. + -gdb has quite good on-line help, as well as -a set of info pages, so this section will concentrate on a few of the -basic commands. + to the file. Once you have done this, you can type + info and then select + make from the menu (or in + Emacs, do C-h + i). + + -Finally, if you find its text-based command-prompt style -off-putting, there's a graphical front-end for it xxgdb -in the ports collection. + + Debugging -This section is intended to be an introduction to using -gdb and does not cover specialised topics such as -debugging the kernel. - - + + The Debugger - -Running a program in the debugger + The debugger that comes with FreeBSD is called + gdb (GNU + debugger). You start it up by typing -You'll need to have compiled the program with the - option to get the most out of using -gdb. It will work without, but you'll only see the -name of the function you're in, instead of the source code. If you -see a line like: - -… (no debugging symbols found) …when -gdb starts up, you'll know that the program wasn't -compiled with the option. - -At the gdb prompt, type break -main. This will tell the debugger to skip over the -preliminary set-up code in the program and start at the beginning of -your code. Now type run to start the -program—it will start at the beginning of the set-up code and -then get stopped by the debugger when it calls -main(). (If you've ever wondered where -main() gets called from, now you know!). + &prompt.user; gdb progname + -You can now step through the program, a line at a time, by -pressing n. If you get to a function call, you can -step into it by pressing s. Once you're in a -function call, you can return from stepping into a function call by -pressing f. You can also use up and -down to take a quick look at the caller. + although most people prefer to run it inside + Emacs. You can do this by: -Here's a simple example of how to spot a mistake in a program -with gdb. This is our program (with a deliberate -mistake): - -#include <stdio.h> + M-x gdb RET progname RET + + + Using a debugger allows you to run the program under more + controlled circumstances. Typically, you can step through the + program a line at a time, inspect the value of variables, + change them, tell the debugger to run up to a certain point + and then stop, and so on. You can even attach to a program + that's already running, or load a core file to investigate why + the program crashed. It's even possible to debug the kernel, + though that's a little trickier than the user applications + we'll be discussing in this section. + + gdb has quite good on-line help, as + well as a set of info pages, so this section will concentrate + on a few of the basic commands. + + Finally, if you find its text-based command-prompt style + off-putting, there's a graphical front-end for it xxgdb in the ports + collection. + + This section is intended to be an introduction to using + gdb and does not cover specialised topics + such as debugging the kernel. + + + + Running a program in the debugger + + You'll need to have compiled the program with the + option to get the most out of using + gdb. It will work without, but you'll only + see the name of the function you're in, instead of the source + code. If you see a line like: + + … (no debugging symbols found) … + + + when gdb starts up, you'll know that + the program wasn't compiled with the + option. + + At the gdb prompt, type + break main. This will tell the + debugger to skip over the preliminary set-up code in the + program and start at the beginning of your code. Now type + run to start the program—it will + start at the beginning of the set-up code and then get stopped + by the debugger when it calls main(). + (If you've ever wondered where main() + gets called from, now you know!). + + You can now step through the program, a line at a time, by + pressing n. If you get to a function call, + you can step into it by pressing s. Once + you're in a function call, you can return from stepping into a + function call by pressing f. You can also + use up and down to take + a quick look at the caller. + + Here's a simple example of how to spot a mistake in a + program with gdb. This is our program + (with a deliberate mistake): + + #include <stdio.h> int bazz(int anint); @@ -1158,21 +1394,26 @@ main() { int bazz(int anint) { printf("You gave me %d\n", anint); return anint; -} - -This program sets i to be 5 -and passes it to a function bazz() which prints -out the number we gave it. +} + -When we compile and run the program we get - -&prompt.user; cc -g -o temp temp.c + This program sets i to be + 5 and passes it to a function + bazz() which prints out the number we + gave it. + + When we compile and run the program we get + + &prompt.user; cc -g -o temp temp.c &prompt.user; ./temp This is my program -anint = 4231 - -That wasn't what we expected! Time to see what's going -on!&prompt.user; gdb temp +anint = 4231 + + + That wasn't what we expected! Time to see what's going + on! + + &prompt.user; gdb temp GDB is free software and you are welcome to distribute copies of it under certain conditions; type "show copying" to see the conditions. There is absolutely no warranty for GDB; type "show warranty" for details. @@ -1187,71 +1428,78 @@ Breakpoint 1, main () at temp.c:9 gdb stops This is my program Program prints out (gdb) s step into bazz() bazz (anint=4231) at temp.c:17 gdb displays stack frame -(gdb) +(gdb) + - -Hang on a minute! How did anint get to be -4231? Didn't we set it to be 5 -in main()? Let's move up to -main() and have a look. + Hang on a minute! How did anint get to be + 4231? Didn't we set it to be + 5 in main()? Let's + move up to main() and have a look. -(gdb) up Move up call stack + (gdb) up Move up call stack #1 0x1625 in main () at temp.c:11 gdb displays stack frame (gdb) p i Show us the value of i $1 = 4231 gdb displays 4231 - - -Oh dear! Looking at the code, we forgot to initialise -i. We meant to put - -… + + + Oh dear! Looking at the code, we forgot to initialise + i. We meant to put + + … main() { int i; i = 5; printf("This is my program\n"); -&hellip - -but we left the i=5; line out. As we didn't -initialise i, it had whatever number happened to be -in that area of memory when the program ran, which in this case -happened to be 4231. +&hellip + -gdb displays the stack frame -every time we go into or out of a function, even if we're using -up and down to move around the -call stack. This shows the name of the function and the values of -its arguments, which helps us keep track of where we are and what's -going on. (The stack is a storage area where the program stores -information about the arguments passed to functions and where to go -when it returns from a function call). + but we left the i=5; line out. As we + didn't initialise i, it had whatever number + happened to be in that area of memory when the program ran, + which in this case happened to be + 4231. - + + gdb displays the stack frame every + time we go into or out of a function, even if we're using + up and down to move + around the call stack. This shows the name of the function + and the values of its arguments, which helps us keep track + of where we are and what's going on. (The stack is a + storage area where the program stores information about the + arguments passed to functions and where to go when it + returns from a function call). + + - -Examining a core file + + Examining a core file -A core file is basically a file which contains the complete -state of the process when it crashed. In the good old -days, programmers had to print out hex listings of core files -and sweat over machine code manuals, but now life is a bit easier. -Incidentally, under FreeBSD and other 4.4BSD systems, a core file is -called progname.core instead of just -core, to make it clearer which program a core -file belongs to. + A core file is basically a file which contains the + complete state of the process when it crashed. In the + good old days, programmers had to print out hex + listings of core files and sweat over machine code manuals, + but now life is a bit easier. Incidentally, under FreeBSD and + other 4.4BSD systems, a core file is called + progname.core instead of just + core, to make it clearer which program a + core file belongs to. -To examine a core file, start up gdb in the -usual way. Instead of typing break or -run, type - -(gdb) core progname.core - -If you're not in the same directory as the core file, you'll have to -do dir /path/to/core/file first. - -You should see something like this: - -&prompt.user; gdb a.out + To examine a core file, start up gdb in + the usual way. Instead of typing break or + run, type + + (gdb) core progname.core + + + If you're not in the same directory as the core file, + you'll have to do dir + /path/to/core/file first. + + You should see something like this: + + &prompt.user; gdb a.out GDB is free software and you are welcome to distribute copies of it under certain conditions; type "show copying" to see the conditions. There is absolutely no warranty for GDB; type "show warranty" for details. @@ -1261,52 +1509,60 @@ Core was generated by `a.out'. Program terminated with signal 11, Segmentation fault. Cannot access memory at address 0x7020796d. #0 0x164a in bazz (anint=0x5) at temp.c:17 -(gdb) - -In this case, the program was called -a.out, so the core file is called -a.out.core. We can see that the program crashed -due to trying to access an area in memory that was not available to -it in a function called bazz. +(gdb) + -Sometimes it's useful to be able to see how a function was -called, as the problem could have occurred a long way up the call -stack in a complex program. The bt command causes -gdb to print out a back-trace of the call -stack: - -(gdb) bt + In this case, the program was called + a.out, so the core file is called + a.out.core. We can see that the program + crashed due to trying to access an area in memory that was not + available to it in a function called + bazz. + + Sometimes it's useful to be able to see how a function was + called, as the problem could have occurred a long way up the + call stack in a complex program. The bt + command causes gdb to print out a + back-trace of the call stack: + + (gdb) bt #0 0x164a in bazz (anint=0x5) at temp.c:17 #1 0xefbfd888 in end () #2 0x162c in main () at temp.c:11 -(gdb)The end() function is called when -a program crashes; in this case, the bazz() -function was called from main(). +(gdb) + - + The end() function is called when a + program crashes; in this case, the bazz() + function was called from main(). + - -Attaching to a running program + + Attaching to a running program -One of the neatest features about gdb is -that it can attach to a program that's already running. Of course, -that assumes you have sufficient permissions to do so. A common -problem is when you are stepping through a program that forks, and -you want to trace the child, but the debugger will only let you trace -the parent. + One of the neatest features about gdb + is that it can attach to a program that's already running. Of + course, that assumes you have sufficient permissions to do so. + A common problem is when you are stepping through a program + that forks, and you want to trace the child, but the debugger + will only let you trace the parent. -What you do is start up another gdb, use -ps to find the process ID for the child, and -do(gdb) attach pid - -in gdb, and then debug as usual. - -That's all very well, you're probably thinking, -but by the time I've done that, the child process will be over -the hill and far away. Fear not, gentle reader, here's how to -do it (courtesy of the gdb info pages): - -&hellip + What you do is start up another gdb, + use ps to find the process ID for the + child, and do + + (gdb) attach pid + + + in gdb, and then debug as usual. + + That's all very well, you're probably + thinking, but by the time I've done that, the child + process will be over the hill and far away. Fear + not, gentle reader, here's how to do it (courtesy of the + gdb info pages): + + &hellip if ((pid = fork()) < 0) /* _Always_ check this */ error(); else if (pid == 0) { /* child */ @@ -1316,223 +1572,275 @@ else if (pid == 0) { /* child */ sleep(10); /* Wait until someone attaches to us */ &hellip } else { /* parent */ - &hellip - -Now all you have to do is attach to the child, set -PauseMode to 0, and -wait for the sleep() call to return! - - - + &hellip + - -Using Emacs as a Development Environment + Now all you have to do is attach to the child, set + PauseMode to 0, and wait + for the sleep() call to return! + + - -Emacs + + Using Emacs as a Development Environment -Unfortunately, Unix systems don't come with the kind of -everything-you-ever-wanted-and-lots-more-you-didn't-in-one-gigantic-package -integrated development environments that other systems -have.At least, not unless you pay out very large sums -of money. However, it is possible to set up your -own environment. It may not be as pretty, and it may not be quite as -integrated, but you can set it up the way you want it. And it's free. -And you have the source to it. + + Emacs -The key to it all is Emacs. Now there are some people who -loathe it, but many who love it. If you're one of the former, I'm -afraid this section will hold little of interest to you. Also, you'll -need a fair amount of memory to run it—I'd recommend 8MB in -text mode and 16MB in X as the bare minimum to get reasonable -performance. + Unfortunately, Unix systems don't come with the kind of + everything-you-ever-wanted-and-lots-more-you-didn't-in-one-gigantic-package + integrated development environments that other systems + have. -Emacs is basically a highly customisable editor—indeed, -it has been customised to the point where it's more like an operating -system than an editor! Many developers and sysadmins do in fact -spend practically all their time working inside Emacs, leaving it -only to log out. + + At least, not unless you pay out very large sums of + money. + -It's impossible even to summarise everything Emacs can do here, but -here are some of the features of interest to developers: - - + However, it is possible to set up your own environment. It + may not be as pretty, and it may not be quite as integrated, + but you can set it up the way you want it. And it's free. + And you have the source to it. -Very powerful editor, allowing search-and-replace on -both strings and regular expressions (patterns), jumping to start/end -of block expression, etc, etc. + The key to it all is Emacs. Now there are some people who + loathe it, but many who love it. If you're one of the former, + I'm afraid this section will hold little of interest to you. + Also, you'll need a fair amount of memory to run it—I'd + recommend 8MB in text mode and 16MB in X as the bare minimum + to get reasonable performance. -Pull-down menus and online help. + Emacs is basically a highly customisable + editor—indeed, it has been customised to the point where + it's more like an operating system than an editor! Many + developers and sysadmins do in fact spend practically all + their time working inside Emacs, leaving it only to log + out. -Language-dependent syntax highlighting and -indentation. + It's impossible even to summarise everything Emacs can do + here, but here are some of the features of interest to + developers: -Completely customisable. + + + Very powerful editor, allowing search-and-replace on + both strings and regular expressions (patterns), jumping + to start/end of block expression, etc, etc. + -You can compile and debug programs within -Emacs. + + Pull-down menus and online help. + -On a compilation error, you can jump to the offending -line of source code. + + Language-dependent syntax highlighting and + indentation. + -Friendly-ish front-end to the info -program used for reading GNU hypertext documentation, including the -documentation on Emacs itself. + + Completely customisable. + -Friendly front-end to gdb, -allowing you to look at the source code as you step through your -program. + + You can compile and debug programs within + Emacs. + -You can read Usenet news and mail while your program -is compiling. + + On a compilation error, you can jump to the offending + line of source code. + -And doubtless many more that I've overlooked. + + Friendly-ish front-end to the info + program used for reading GNU hypertext documentation, + including the documentation on Emacs itself. + -Emacs can be installed on FreeBSD using the Emacs -port. + + Friendly front-end to gdb, allowing + you to look at the source code as you step through your + program. + -Once it's installed, start it up and do C-h -t to read an Emacs tutorial—that means hold down -the control key, press h, let go of -the control key, and then press t. -(Alternatively, you can you use the mouse to select Emacs -Tutorial from the Help menu). + + You can read Usenet news and mail while your program + is compiling. + + -Although Emacs does have menus, it's well worth learning the -key bindings, as it's much quicker when you're editing something to -press a couple of keys than to try and find the mouse and then click -on the right place. And, when you're talking to seasoned Emacs users, -you'll find they often casually throw around expressions like -M-x replace-s RET foo RET bar RET -so it's useful to know what they mean. And in any case, Emacs has far -too many useful functions for them to all fit on the menu -bars. + And doubtless many more that I've overlooked. -Fortunately, it's quite easy to pick up the key-bindings, as -they're displayed next to the menu item. My advice is to use the -menu item for, say, opening a file until you understand how it works -and feel confident with it, then try doing C-x C-f. When you're happy -with that, move on to another menu command. + Emacs can be installed on FreeBSD using the Emacs + port. -If you can't remember what a particular combination of keys -does, select Describe Key from the -Help menu and type it in—Emacs will tell you -what it does. You can also use the Command -Apropos menu item to find out all the commands which -contain a particular word in them, with the key binding next to -it. + Once it's installed, start it up and do C-h + t to read an Emacs tutorial—that means + hold down the control key, press + h, let go of the control + key, and then press t. (Alternatively, you + can you use the mouse to select Emacs + Tutorial from the Help + menu). -By the way, the expression above means hold down the -Meta key, press x, release the -Meta key, type replace-s -(short for replace-string—another feature of -Emacs is that you can abbreviate commands), press the -return key, type foo (the -string you want replaced), press the return key, -type bar (the string you want to replace foo with) -and press return again. Emacs will then do the -search-and-replace operation you've just requested. + Although Emacs does have menus, it's well worth learning + the key bindings, as it's much quicker when you're editing + something to press a couple of keys than to try and find the + mouse and then click on the right place. And, when you're + talking to seasoned Emacs users, you'll find they often + casually throw around expressions like M-x + replace-s RET foo RET bar RET so it's + useful to know what they mean. And in any case, Emacs has far + too many useful functions for them to all fit on the menu + bars. -If you're wondering what on earth the Meta key -is, it's a special key that many Unix workstations have. -Unfortunately, PC's don't have one, so it's usually the -alt key (or if you're unlucky, the escape -key). + Fortunately, it's quite easy to pick up the key-bindings, + as they're displayed next to the menu item. My advice is to + use the menu item for, say, opening a file until you + understand how it works and feel confident with it, then try + doing C-x C-f. When you're happy with that, move on to + another menu command. -Oh, and to get out of Emacs, do C-x C-c -(that means hold down the control key, press -x, press c and release the -control key). If you have any unsaved files open, -Emacs will ask you if you want to save them. (Ignore the bit in the -documentation where it says C-z is the usual way -to leave Emacs—that leaves Emacs hanging around in the -background, and is only really useful if you're on a system which -doesn't have virtual terminals). + If you can't remember what a particular combination of + keys does, select Describe Key from + the Help menu and type it in—Emacs + will tell you what it does. You can also use the + Command Apropos menu item to find + out all the commands which contain a particular word in them, + with the key binding next to it. - + By the way, the expression above means hold down the + Meta key, press x, release + the Meta key, type + replace-s (short for + replace-string—another feature of + Emacs is that you can abbreviate commands), press the + return key, type foo + (the string you want replaced), press the + return key, type bar (the string you want to + replace foo with) and press + return again. Emacs will then do the + search-and-replace operation you've just requested. - -Configuring Emacs + If you're wondering what on earth the + Meta key is, it's a special key that many + Unix workstations have. Unfortunately, PC's don't have one, + so it's usually the alt key (or if you're + unlucky, the escape key). -Emacs does many wonderful things; some of them are built in, -some of them need to be configured. + Oh, and to get out of Emacs, do C-x C-c + (that means hold down the control key, press + x, press c and release the + control key). If you have any unsaved files + open, Emacs will ask you if you want to save them. (Ignore + the bit in the documentation where it says + C-z is the usual way to leave + Emacs—that leaves Emacs hanging around in the + background, and is only really useful if you're on a system + which doesn't have virtual terminals). + -Instead of using a proprietary macro language for -configuration, Emacs uses a version of Lisp specially adapted for -editors, known as Emacs Lisp. This can be quite useful if you want to -go on and learn something like Common Lisp, as it's considerably -smaller than Common Lisp (although still quite big!). + + Configuring Emacs -The best way to learn Emacs Lisp is to download the Emacs -Tutorial + Emacs does many wonderful things; some of them are built + in, some of them need to be configured. -However, there's no need to actually know any Lisp to get -started with configuring Emacs, as I've included a sample -.emacs file, which should be enough to get you -started. Just copy it into your home directory and restart Emacs if -it's already running; it will read the commands from the file and -(hopefully) give you a useful basic setup. + Instead of using a proprietary macro language for + configuration, Emacs uses a version of Lisp specially adapted + for editors, known as Emacs Lisp. This can be quite useful if + you want to go on and learn something like Common Lisp, as + it's considerably smaller than Common Lisp (although still + quite big!). - + The best way to learn Emacs Lisp is to download the Emacs + Tutorial - -A sample <filename>.emacs</filename> file + However, there's no need to actually know any Lisp to get + started with configuring Emacs, as I've included a sample + .emacs file, which should be enough to + get you started. Just copy it into your home directory and + restart Emacs if it's already running; it will read the + commands from the file and (hopefully) give you a useful basic + setup. + -Unfortunately, there's far too much here to explain it in detail; -however there are one or two points worth mentioning. - - + + A sample <filename>.emacs</filename> file -Everything beginning with a ; is a -comment and is ignored by Emacs. + Unfortunately, there's far too much here to explain it in + detail; however there are one or two points worth + mentioning. -In the first line, the --*- Emacs-Lisp -*- is so that we can -edit the .emacs file itself within Emacs and get -all the fancy features for editing Emacs Lisp. Emacs usually tries to -guess this based on the filename, and may not get it right for -.emacs. + + + Everything beginning with a ; is a comment + and is ignored by Emacs. + -The tab key is bound to an -indentation function in some modes, so when you press the tab key, it -will indent the current line of code. If you want to put a -tab character in whatever you're writing, hold the -control key down while you're pressing the -tab key. + + In the first line, the + -*- Emacs-Lisp -*- is so that + we can edit the .emacs file itself + within Emacs and get all the fancy features for editing + Emacs Lisp. Emacs usually tries to guess this based on + the filename, and may not get it right for + .emacs. + -This file supports syntax highlighting for C, C++, -Perl, Lisp and Scheme, by guessing the language from the -filename. + + The tab key is bound to an + indentation function in some modes, so when you press the + tab key, it will indent the current line of code. If you + want to put a tab character in whatever + you're writing, hold the control key down + while you're pressing the tab key. + -Emacs already has a pre-defined function called -next-error. In a compilation output window, this -allows you to move from one compilation error to the next by doing -M-n; we define a complementary function, -previous-error, that allows you to go to a -previous error by doing M-p. The nicest feature of -all is that C-c C-c will open up the source file -in which the error occurred and jump to the appropriate -line. + + This file supports syntax highlighting for C, C++, + Perl, Lisp and Scheme, by guessing the language from the + filename. + - We enable Emacs's ability to act as a server, so -that if you're doing something outside Emacs and you want to edit a -file, you can just type in - -&prompt.user; emacsclient filename - -and then you can edit the file in your Emacs!Many -Emacs users set their EDITOR environment to -emacsclient so this happens every time they need -to edit a file. + + Emacs already has a pre-defined function called + next-error. In a compilation output + window, this allows you to move from one compilation error + to the next by doing M-n; we define a + complementary function, + previous-error, that allows you to go + to a previous error by doing M-p. The + nicest feature of all is that C-c C-c + will open up the source file in which the error occurred + and jump to the appropriate line. + - - - -A sample <filename>.emacs</filename> file -;; -*-Emacs-Lisp-*- + + We enable Emacs's ability to act as a server, so that + if you're doing something outside Emacs and you want to + edit a file, you can just type in + + &prompt.user; emacsclient filename + + + and then you can edit the file in your + Emacs! + + + Many Emacs users set their EDITOR environment to + emacsclient so this happens every + time they need to edit a file. + + + + + + A sample <filename>.emacs</filename> file + + ;; -*-Emacs-Lisp-*- ;; This file is designed to be re-evaled; use the variable first-time ;; to avoid any problems with this. @@ -1813,127 +2121,148 @@ in font-lock-auto-mode-list" ;; All done (message "All done, %s%s" (user-login-name) ".") - - - - + + + - -Extending the Range of Languages Emacs Understands + + Extending the Range of Languages Emacs Understands -Now, this is all very well if you only want to program in the -languages already catered for in the .emacs file -(C, C++, Perl, Lisp and Scheme), but what happens if a new language -called whizbang comes out, full of exciting -features? + Now, this is all very well if you only want to program in + the languages already catered for in the + .emacs file (C, C++, Perl, Lisp and + Scheme), but what happens if a new language called + whizbang comes out, full of exciting + features? -The first thing to do is find out if whizbang -comes with any files that tell Emacs about the language. These -usually end in .el, short for Emacs -Lisp. For example, if whizbang is a FreeBSD -port, we can locate these files by doing - -&prompt.user; find /usr/ports/lang/whizbang -name "*.el" -print - -and install them by copying them into the Emacs site Lisp directory. On -FreeBSD 2.1.0-RELEASE, this is -/usr/local/share/emacs/site-lisp. + The first thing to do is find out if whizbang comes with + any files that tell Emacs about the language. These usually + end in .el, short for Emacs + Lisp. For example, if whizbang is a FreeBSD port, we + can locate these files by doing -So for example, if the output from the find command was - -/usr/ports/lang/whizbang/work/misc/whizbang.el - -we would do - -&prompt.root; cp /usr/ports/lang/whizbang/work/misc/whizbang.el /usr/local/share/emacs/site-lisp - -Next, we need to decide what extension whizbang source files -have. Let's say for the sake of argument that they all end in -.wiz. We need to add an entry to our -.emacs file to make sure Emacs will be able to -use the information in whizbang.el. + &prompt.user; find /usr/ports/lang/whizbang -name "*.el" -print + -Find the auto-mode-alist entry in -.emacs and add a line for whizbang, such -as: - -… + and install them by copying them into the Emacs site Lisp + directory. On FreeBSD 2.1.0-RELEASE, this is + /usr/local/share/emacs/site-lisp. + + So for example, if the output from the find command + was + + /usr/ports/lang/whizbang/work/misc/whizbang.el + + + we would do + + &prompt.root; cp /usr/ports/lang/whizbang/work/misc/whizbang.el /usr/local/share/emacs/site-lisp + + + Next, we need to decide what extension whizbang source + files have. Let's say for the sake of argument that they all + end in .wiz. We need to add an entry to + our .emacs file to make sure Emacs will + be able to use the information in + whizbang.el. + + Find the auto-mode-alist entry in + .emacs and add a line for whizbang, such + as: + + … ("\\.lsp$" . lisp-mode) ("\\.wiz$" . whizbang-mode) ("\\.scm$" . scheme-mode) -… - -This means that Emacs will automatically go into -whizbang-mode when you edit a file ending in -.wiz. +… + -Just below this, you'll find the -font-lock-auto-mode-list entry. Add -whizbang-mode to it like so: - -;; Auto font lock mode + This means that Emacs will automatically go into + whizbang-mode when you edit a file ending + in .wiz. + + Just below this, you'll find the + font-lock-auto-mode-list entry. Add + whizbang-mode to it like so: + + ;; Auto font lock mode (defvar font-lock-auto-mode-list (list 'c-mode 'c++-mode 'c++-c-mode 'emacs-lisp-mode 'whizbang-mode 'lisp-mode 'perl-mode 'scheme-mode) - "List of modes to always start in font-lock-mode") - -This means that Emacs will always enable -font-lock-mode (ie syntax highlighting) when -editing a .wiz file. + "List of modes to always start in font-lock-mode") + -And that's all that's needed. If there's anything else you want -done automatically when you open up a .wiz file, -you can add a whizbang-mode hook (see -my-scheme-mode-hook for a simple example that -adds auto-indent). - - - + This means that Emacs will always enable + font-lock-mode (ie syntax highlighting) + when editing a .wiz file. - -Further Reading + And that's all that's needed. If there's anything else + you want done automatically when you open up a + .wiz file, you can add a + whizbang-mode hook (see + my-scheme-mode-hook for a simple example + that adds auto-indent). + + - -Brian Harvey and Matthew Wright -Simply Scheme -MIT 1994. -ISBN 0-262-08226-8 + + Further Reading -Randall Schwartz -Learning Perl -O'Reilly 1993 -ISBN 1-56592-042-2 + + + Brian Harvey and Matthew Wright + Simply Scheme + MIT 1994. + ISBN 0-262-08226-8 + -Patrick Henry Winston and Berthold Klaus Paul Horn -Lisp (3rd Edition) -Addison-Wesley 1989 -ISBN 0-201-08319-1 + + Randall Schwartz + Learning Perl + O'Reilly 1993 + ISBN 1-56592-042-2 + -Brian W. Kernighan and Rob Pike -The Unix Programming Environment -Prentice-Hall 1984 -ISBN 0-13-937681-X + + Patrick Henry Winston and Berthold Klaus Paul Horn + Lisp (3rd Edition) + Addison-Wesley 1989 + ISBN 0-201-08319-1 + -Brian W. Kernighan and Dennis M. Ritchie -The C Programming Language (2nd Edition) -Prentice-Hall 1988 -ISBN 0-13-110362-8 + + Brian W. Kernighan and Rob Pike + The Unix Programming Environment + Prentice-Hall 1984 + ISBN 0-13-937681-X + -Bjarne Stroustrup -The C++ Programming Language -Addison-Wesley 1991 -ISBN 0-201-53992-6 + + Brian W. Kernighan and Dennis M. Ritchie + The C Programming Language (2nd Edition) + Prentice-Hall 1988 + ISBN 0-13-110362-8 + -W. Richard Stevens -Advanced Programming in the Unix Environment -Addison-Wesley 1992 -ISBN 0-201-56317-7 + + Bjarne Stroustrup + The C++ Programming Language + Addison-Wesley 1991 + ISBN 0-201-53992-6 + -W. Richard Stevens -Unix Network Programming -Prentice-Hall 1990 -ISBN 0-13-949876-1 + + W. Richard Stevens + Advanced Programming in the Unix Environment + Addison-Wesley 1992 + ISBN 0-201-56317-7 + - - - + + W. Richard Stevens + Unix Network Programming + Prentice-Hall 1990 + ISBN 0-13-949876-1 + + +
diff --git a/en_US.ISO_8859-1/articles/programming-tools/article.sgml b/en_US.ISO_8859-1/articles/programming-tools/article.sgml index 18badea392..d32b3869f8 100644 --- a/en_US.ISO_8859-1/articles/programming-tools/article.sgml +++ b/en_US.ISO_8859-1/articles/programming-tools/article.sgml @@ -1,560 +1,677 @@ - +
- - -A User's Guide to FreeBSD Programming Tools - - - -James -Raynard - -
-jraynard@FreeBSD.org -
- - - -August 17, 1997 - - -1997 -James Raynard - - -This document is an introduction to using some of the programming -tools supplied with FreeBSD, although much of it will be applicable to -many other versions of Unix. It does not attempt to describe -coding in any detail. Most of the document assumes little or no -previous programming knowledge, although it is hoped that most -programmers will find something of value in it - - - -Introduction<anchor id=foo> - -FreeBSD offers an excellent development environment. Compilers -for C, C++, and Fortran and an assembler come with the basic system, -not to mention a Perl interpreter and classic Unix tools such as -sed and awk. If that is not enough, there are -many more compilers and interpreters in the Ports collection. FreeBSD -is very compatible with standards such as POSIX and -ANSI C, as well with its own BSD heritage, so it is -possible to write applications that will compile and run with little -or no modification on a wide range of platforms. - -However, all this power can be rather overwhelming at first if -you've never written programs on a Unix platform before. This -document aims to help you get up and running, without getting too -deeply into more advanced topics. The intention is that this document -should give you enough of the basics to be able to make some sense of -the documentation. - -Most of the document requires little or no knowledge of -programming, although it does assume a basic competence with using -Unix and a willingness to learn! - - - - -Introduction to Programming - -A program is a set of instructions that tell the computer to do -various things; sometimes the instruction it has to perform depends -on what happened when it performed a previous instruction. This -section gives an overview of the two main ways in which you can give -these instructions, or commands as they are usually -called. One way uses an interpreter, the other a -compiler. As human languages are too difficult for a -computer to understand in an unambiguous way, commands are usually -written in one or other languages specially designed for the -purpose. - - - - -Interpreters - -With an interpreter, the language comes as an environment, where you -type in commands at a prompt and the environment executes them for -you. For more complicated programs, you can type the commands into a -file and get the interpreter to load the file and execute the commands -in it. If anything goes wrong, many interpreters will drop you into a -debugger to help you track down the problem. - -The advantage of this is that you can see the results of your -commands immediately, and mistakes can be corrected readily. The -biggest disadvantage comes when you want to share your programs with -someone. They must have the same interpreter, or you must have some -way of giving it to them, and they need to understand how to use it. -Also users may not appreciate being thrown into a debugger if they -press the wrong key! From a performance point of view, interpreters -can use up a lot of memory, and generally do not generate code as -efficiently as compilers. - -In my opinion, interpreted languages are the best way to start -if you have not done any programming before. This kind of environment -is typically found with languages like Lisp, Smalltalk, Perl and -Basic. It could also be argued that the Unix shell (sh, -csh) is itself an interpreter, and many people do in fact -write shell scripts to help with various -housekeeping tasks on their machine. Indeed, part of the -original Unix philosophy was to provide lots of small utility -programs that could be linked together in shell scripts to perform -useful tasks. - - - - -Interpreters available with FreeBSD - -Here is a list of interpreters that are available as FreeBSD -packages, with a brief discussion of some of the more popular -interpreted languages. - -To get one of these packages, all you need to do is to click on -the hotlink for the package, then run - -&prompt.root; pkg_add package name - -as root. Obviously, you will need to have a fully functional FreeBSD -2.1.0 or later system for the package to work! - - -BASIC - -Short for Beginner's All-purpose Symbolic Instruction -Code. Developed in the 1950s for teaching University students to -program and provided with every self-respecting personal computer in -the 1980s, BASIC has been the first programming language -for many programmers. It's also the foundation for Visual -Basic. - -The Bywater -Basic Interpreter and the Phil -Cockroft's Basic Interpreter (formerly Rabbit Basic) are -available as FreeBSD FreeBSD -packages - - - -Lisp -A language that was developed in the late 1950s as an alternative to -the number-crunching languages that were popular at the time. -Instead of being based on numbers, Lisp is based on lists; in fact -the name is short for List Processing. Very popular in AI -(Artificial Intelligence) circles. - -Lisp is an extremely powerful and sophisticated language, but -can be rather large and unwieldy. - -FreeBSD has GNU -Common Lisp available as a package. - - - - -Perl -Very popular with system administrators for writing -scripts; also often used on World Wide Web servers for writing CGI -scripts. - -Version 4, which is probably still the most widely-used -version, comes with FreeBSD; the newer Perl -Version 5 is available as a package. - - - - -Scheme -A dialect of Lisp that is rather more compact and -cleaner than Common Lisp. Popular in Universities as it is simple -enough to teach to undergraduates as a first language, while it has a -high enough level of abstraction to be used in research work. - -FreeBSD has packages of the -Elk Scheme Interpreter, the -MIT Scheme Interpreter and the -SCM Scheme Interpreter. - - - - -Icon -The Icon Programming Language. - - - -Logo -Brian Harvey's LOGO Interpreter. - - - -Python -The Python Object-Oriented Programming Language - - - - - - - - -Compilers - -Compilers are rather different. First of all, you write your -code in a file (or files) using an editor. You then run the compiler -and see if it accepts your program. If it did not compile, grit your -teeth and go back to the editor; if it did compile and gave you a -program, you can run it either at a shell command prompt or in a -debugger to see if it works properly.If you run it in -the shell, you may get a core dump. - -Obviously, this is not quite as direct as using an interpreter. -However it allows you to do a lot of things which are very difficult -or even impossible with an interpreter, such as writing code which -interacts closely with the operating system—or even writing -your own operating system! It's also useful if you need to write very -efficient code, as the compiler can take its time and optimise the -code, which would not be acceptable in an interpreter. And -distributing a program written for a compiler is usually more -straightforward than one written for an interpreter—you can just -give them a copy of the executable, assuming they have the same -operating system as you. - -Compiled languages include Pascal, C and C++. C and C++ are rather -unforgiving languages, and best suited to more experienced -programmers; Pascal, on the other hand, was designed as an educational -language, and is quite a good language to start with. Unfortunately, -FreeBSD doesn't have any Pascal support, except for a Pascal-to-C -converter in the ports. - -As the edit-compile-run-debug cycle is rather tedious when -using separate programs, many commercial compiler makers have -produced Integrated Development Environments (IDEs -for short). FreeBSD does not have an IDE as such; however -it is possible to use Emacs for this purpose. This is discussed in -. - - - - - -Compiling with <command>cc</command> - -This section deals only with the GNU compiler for C and C++, -since that comes with the base FreeBSD system. It can be invoked by -either cc or gcc. The details of producing a -program with an interpreter vary considerably between interpreters, -and are usually well covered in the documentation and on-line help -for the interpreter. - -Once you've written your masterpiece, the next step is to convert it -into something that will (hopefully!) run on FreeBSD. This usually -involves several steps, each of which is done by a separate -program. - - -Pre-process your source code to remove comments and do other -tricks like expanding macros in C. - - -Check the syntax of your code to see if you have obeyed the -rules of the language. If you have not, it will complain! - - -Convert the source code into assembly -language—this is very close to machine code, but still -understandable by humans. Allegedly.To be strictly -accurate, cc converts the source code into its own, -machine-independent p-code instead of assembly language -at this stage. - -Convert the assembly language into machine -code—yep, we are talking bits and bytes, ones and zeros -here. - -Check that you have used things like functions and global -variables in a consistent way. For example, if you have called a -non-existent function, it will complain. - -If you are trying to produce an executable from several -source code files, work out how to fit them all together. - -Work out how to produce something that the system's run-time -loader will be able to load into memory and run. - -Finally, write the executable on the file -system. - - - -The word compiling is often used to refer to just -steps 1 to 4—the others are referred to as -linking. Sometimes step 1 is referred to as -pre-processing and steps 3-4 as -assembling. - -Fortunately, almost all this detail is hidden from you, as -cc is a front end that manages calling all these programs -with the right arguments for you; simply typing - -&prompt.user; cc foobar.c - -will cause foobar.c to be compiled by all the -steps above. If you have more than one file to compile, just do -something like - -&prompt.user; cc foo.c bar.c - -Note that the syntax checking is just that—checking the -syntax. It will not check for any logical mistakes you may have made, -like putting the program into an infinite loop, or using a bubble -sort when you meant to use a binary sort.In case you -didn't know, a binary sort is an efficient way of sorting things into -order and a bubble sort isn't. - -There are lots and lots of options for cc, which -are all in the man page. Here are a few of the most important ones, -with examples of how to use them. - - - - -The output name of the file. If you do not use this -option, cc will produce an executable called -a.out.The reasons for this are buried in -the mists of history. - - -&prompt.user; cc foobar.c executable is a.out -&prompt.user; cc -o foobar foobar.c executable is foobar - - - - - -Just compile the file, do not link it. Useful for toy -programs where you just want to check the syntax, or if you are using -a Makefile. - - -&prompt.user; cc -c foobar.c - - -This will produce an object file (not an -executable) called foobar.o. This can be linked -together with other object files into an executable. - - - - - - -Create a debug version of the executable. This makes -the compiler put information into the executable about which line of -which source file corresponds to which function call. A debugger can -use this information to show the source code as you step through the -program, which is very useful; the disadvantage -is that all this extra information makes the program much bigger. -Normally, you compile with while you are -developing a program and then compile a release -version without when you're satisfied it -works properly. - - -&prompt.user; cc -g foobar.c - - -This will produce a debug version of the -program.Note, we didn't use the -flag to specify the executable name, so we will get an executable -called a.out. Producing a debug version called -foobar is left as an exercise for the -reader! - - - - - - -Create an optimised version of the executable. The -compiler performs various clever tricks to try and produce an -executable that runs faster than normal. You can add a number after -the to specify a higher level of optimisation, -but this often exposes bugs in the compiler's optimiser. For -instance, the version of cc that comes with the -2.1.0 release of FreeBSD is known to produce bad code with the - option in some circumstances. - -Optimisation is usually only turned on when compiling a release -version. - - -&prompt.user; cc -O -o foobar foobar.c - - -This will produce an optimised version of -foobar. - - - - - -The following three flags will force cc to -check that your code complies to the relevant international standard, -often referred to as the ANSI standard, though -strictly speaking it is an ISO standard. - - - - - -Enable all the warnings which the authors of -cc believe are worthwhile. Despite the name, it -will not enable all the warnings cc is capable -of. - - - - - - -Turn off most, but not all, of the non-ANSI C -features provided by cc. Despite the name, it does -not guarantee strictly that your code will comply to the -standard. - - - - - - - -Turn off all -cc's non-ANSI C features. - - - - - -Without these flags, cc will allow you to -use some of its non-standard extensions to the standard. Some of -these are very useful, but will not work with other compilers—in -fact, one of the main aims of the standard is to allow people to -write code that will work with any compiler on any system. This is -known as portable code. - -Generally, you should try to make your code as portable as -possible, as otherwise you may have to completely re-write the -program later to get it to work somewhere else—and who knows -what you may be using in a few years time? - - -&prompt.user; cc -Wall -ansi -pedantic -o foobar foobar.c - - -This will produce an executable foobar -after checking foobar.c for standard -compliance. - - - - - -Specify a function library to be used during when -linking. - -The most common example of this is when compiling a program that -uses some of the mathematical functions in C. Unlike most other -platforms, these are in a separate library from the standard C one -and you have to tell the compiler to add it. - -The rule is that if the library is called -libsomething.a, you -give cc the argument -. For example, -the math library is libm.a, so you give -cc the argument . A common -gotcha with the math library is that it has to be the -last library on the command line. - - -&prompt.user; cc -o foobar foobar.c -lm - - -This will link the math library functions into -foobar. - -If you are compiling C++ code, you need to add -, or if you are using -FreeBSD 2.2 or later, to the command line argument to link the C++ -library functions. Alternatively, you can run c++ -instead of cc, which does this for you. -c++ can also be invoked as g++ -on FreeBSD. - - -&prompt.user; cc -o foobar foobar.cc -lg++ For FreeBSD 2.1.6 and earlier + + A User's Guide to FreeBSD Programming Tools + + + + James + + Raynard + + +
+ jraynard@FreeBSD.org +
+ + + + + August 17, 1997 + + + 1997 + James Raynard + + + + This document is an introduction to using some of the + programming tools supplied with FreeBSD, although much of it + will be applicable to many other versions of Unix. It does + not attempt to describe coding in any + detail. Most of the document assumes little or no previous + programming knowledge, although it is hoped that most + programmers will find something of value in it + + + + + Introduction<anchor id=foo> + + FreeBSD offers an excellent development environment. + Compilers for C, C++, and Fortran and an assembler come with the + basic system, not to mention a Perl interpreter and classic Unix + tools such as sed and awk. If that is + not enough, there are many more compilers and interpreters in + the Ports collection. FreeBSD is very compatible with standards + such as POSIX and ANSI C, as well with + its own BSD heritage, so it is possible to write applications + that will compile and run with little or no modification on a + wide range of platforms. + + However, all this power can be rather overwhelming at first + if you've never written programs on a Unix platform before. + This document aims to help you get up and running, without + getting too deeply into more advanced topics. The intention is + that this document should give you enough of the basics to be + able to make some sense of the documentation. + + Most of the document requires little or no knowledge of + programming, although it does assume a basic competence with + using Unix and a willingness to learn! + + + + Introduction to Programming + + A program is a set of instructions that tell the computer to + do various things; sometimes the instruction it has to perform + depends on what happened when it performed a previous + instruction. This section gives an overview of the two main + ways in which you can give these instructions, or + commands as they are usually called. One way + uses an interpreter, the other a + compiler. As human languages are too difficult for + a computer to understand in an unambiguous way, commands are + usually written in one or other languages specially designed for + the purpose. + + + Interpreters + + With an interpreter, the language comes as an environment, + where you type in commands at a prompt and the environment + executes them for you. For more complicated programs, you can + type the commands into a file and get the interpreter to load + the file and execute the commands in it. If anything goes + wrong, many interpreters will drop you into a debugger to help + you track down the problem. + + The advantage of this is that you can see the results of + your commands immediately, and mistakes can be corrected + readily. The biggest disadvantage comes when you want to + share your programs with someone. They must have the same + interpreter, or you must have some way of giving it to them, + and they need to understand how to use it. Also users may not + appreciate being thrown into a debugger if they press the + wrong key! From a performance point of view, interpreters can + use up a lot of memory, and generally do not generate code as + efficiently as compilers. + + In my opinion, interpreted languages are the best way to + start if you have not done any programming before. This kind + of environment is typically found with languages like Lisp, + Smalltalk, Perl and Basic. It could also be argued that the + Unix shell (sh, csh) is itself an + interpreter, and many people do in fact write shell + scripts to help with various + housekeeping tasks on their machine. Indeed, part + of the original Unix philosophy was to provide lots of small + utility programs that could be linked together in shell + scripts to perform useful tasks. + + + + Interpreters available with FreeBSD + + Here is a list of interpreters that are available as + FreeBSD + packages, with a brief discussion of some of the + more popular interpreted languages. + + To get one of these packages, all you need to do is to + click on the hotlink for the package, then run + + &prompt.root; pkg_add package name + + + as root. Obviously, you will need to have a fully + functional FreeBSD 2.1.0 or later system for the package to + work! + + + + BASIC + + + Short for Beginner's All-purpose Symbolic + Instruction Code. Developed in the 1950s for teaching + University students to program and provided with every + self-respecting personal computer in the 1980s, + BASIC has been the first programming + language for many programmers. It's also the foundation + for Visual Basic. + + The Bywater + Basic Interpreter and the Phil + Cockroft's Basic Interpreter (formerly Rabbit + Basic) are available as FreeBSD FreeBSD + packages + + + + + Lisp + + + A language that was developed in the late 1950s as + an alternative to the number-crunching + languages that were popular at the time. Instead of + being based on numbers, Lisp is based on lists; in fact + the name is short for List Processing. + Very popular in AI (Artificial Intelligence) + circles. + + Lisp is an extremely powerful and sophisticated + language, but can be rather large and unwieldy. + + FreeBSD has GNU + Common Lisp available as a package. + + + + + Perl + + + Very popular with system administrators for writing + scripts; also often used on World Wide Web servers for + writing CGI scripts. + + Version 4, which is probably still the most + widely-used version, comes with FreeBSD; the newer + Perl + Version 5 is available as a package. + + + + + Scheme + + + A dialect of Lisp that is rather more compact and + cleaner than Common Lisp. Popular in Universities as it + is simple enough to teach to undergraduates as a first + language, while it has a high enough level of + abstraction to be used in research work. + + FreeBSD has packages of the Elk + Scheme Interpreter, the MIT + Scheme Interpreter and the SCM + Scheme Interpreter. + + + + + Icon + + + The + Icon Programming Language. + + + + + Logo + + + Brian + Harvey's LOGO Interpreter. + + + + + Python + + + The + Python Object-Oriented Programming + Language + + + + + + + Compilers + + Compilers are rather different. First of all, you write + your code in a file (or files) using an editor. You then run + the compiler and see if it accepts your program. If it did + not compile, grit your teeth and go back to the editor; if it + did compile and gave you a program, you can run it either at a + shell command prompt or in a debugger to see if it works + properly. + + + If you run it in the shell, you may get a core + dump. + + + Obviously, this is not quite as direct as using an + interpreter. However it allows you to do a lot of things + which are very difficult or even impossible with an + interpreter, such as writing code which interacts closely with + the operating system—or even writing your own operating + system! It's also useful if you need to write very efficient + code, as the compiler can take its time and optimise the code, + which would not be acceptable in an interpreter. And + distributing a program written for a compiler is usually more + straightforward than one written for an interpreter—you + can just give them a copy of the executable, assuming they + have the same operating system as you. + + Compiled languages include Pascal, C and C++. C and C++ + are rather unforgiving languages, and best suited to more + experienced programmers; Pascal, on the other hand, was + designed as an educational language, and is quite a good + language to start with. Unfortunately, FreeBSD doesn't have + any Pascal support, except for a Pascal-to-C converter in the + ports. + + As the edit-compile-run-debug cycle is rather tedious when + using separate programs, many commercial compiler makers have + produced Integrated Development Environments + (IDEs for short). FreeBSD does not have an + IDE as such; however it is possible to use Emacs + for this purpose. This is discussed in . + + + + + Compiling with <command>cc</command> + + This section deals only with the GNU compiler for C and C++, + since that comes with the base FreeBSD system. It can be + invoked by either cc or gcc. The + details of producing a program with an interpreter vary + considerably between interpreters, and are usually well covered + in the documentation and on-line help for the + interpreter. + + Once you've written your masterpiece, the next step is to + convert it into something that will (hopefully!) run on FreeBSD. + This usually involves several steps, each of which is done by a + separate program. + + + + Pre-process your source code to remove comments and do + other tricks like expanding macros in C. + + + + Check the syntax of your code to see if you have obeyed + the rules of the language. If you have not, it will + complain! + + + + Convert the source code into assembly + language—this is very close to machine code, but still + understandable by humans. Allegedly. + + + To be strictly accurate, cc converts the + source code into its own, machine-independent + p-code instead of assembly language at + this stage. + + + + + Convert the assembly language into machine + code—yep, we are talking bits and bytes, ones and + zeros here. + + + + Check that you have used things like functions and + global variables in a consistent way. For example, if you + have called a non-existent function, it will + complain. + + + + If you are trying to produce an executable from several + source code files, work out how to fit them all + together. + + + + Work out how to produce something that the system's + run-time loader will be able to load into memory and + run. + + + + Finally, write the executable on the file system. + + + + The word compiling is often used to refer to + just steps 1 to 4—the others are referred to as + linking. Sometimes step 1 is referred to as + pre-processing and steps 3-4 as + assembling. + + Fortunately, almost all this detail is hidden from you, as + cc is a front end that manages calling all these + programs with the right arguments for you; simply typing + + &prompt.user; cc foobar.c + + + will cause foobar.c to be compiled by all the + steps above. If you have more than one file to compile, just do + something like + + &prompt.user; cc foo.c bar.c + + + Note that the syntax checking is just that—checking + the syntax. It will not check for any logical mistakes you may + have made, like putting the program into an infinite loop, or + using a bubble sort when you meant to use a binary + sort. + + + In case you didn't know, a binary sort is an efficient + way of sorting things into order and a bubble sort + isn't. + + + There are lots and lots of options for cc, which + are all in the man page. Here are a few of the most important + ones, with examples of how to use them. + + + + + + + The output name of the file. If you do not use this + option, cc will produce an executable called + a.out. + + + The reasons for this are buried in the mists of + history. + + + + &prompt.user; cc foobar.c executable is a.out +&prompt.user; cc -o foobar foobar.c executable is foobar + + + + + + + + + + Just compile the file, do not link it. Useful for toy + programs where you just want to check the syntax, or if + you are using a Makefile. + + + &prompt.user; cc -c foobar.c + + + + This will produce an object file (not an + executable) called foobar.o. This + can be linked together with other object files into an + executable. + + + + + + + + Create a debug version of the executable. This makes + the compiler put information into the executable about + which line of which source file corresponds to which + function call. A debugger can use this information to show + the source code as you step through the program, which is + very useful; the disadvantage is that + all this extra information makes the program much bigger. + Normally, you compile with while you + are developing a program and then compile a release + version without when you're + satisfied it works properly. + + + &prompt.user; cc -g foobar.c + + + + This will produce a debug version of the + program. + + + Note, we didn't use the flag + to specify the executable name, so we will get an + executable called a.out. + Producing a debug version called + foobar is left as an exercise for + the reader! + + + + + + + + + Create an optimised version of the executable. The + compiler performs various clever tricks to try and produce + an executable that runs faster than normal. You can add a + number after the to specify a higher + level of optimisation, but this often exposes bugs in the + compiler's optimiser. For instance, the version of + cc that comes with the 2.1.0 release of + FreeBSD is known to produce bad code with the + option in some circumstances. + + Optimisation is usually only turned on when compiling + a release version. + + + &prompt.user; cc -O -o foobar foobar.c + + + + This will produce an optimised version of + foobar. + + + + + The following three flags will force cc + to check that your code complies to the relevant international + standard, often referred to as the ANSI + standard, though strictly speaking it is an + ISO standard. + + + + + + + Enable all the warnings which the authors of + cc believe are worthwhile. Despite the + name, it will not enable all the warnings + cc is capable of. + + + + + + + + Turn off most, but not all, of the + non-ANSI C features provided by + cc. Despite the name, it does not + guarantee strictly that your code will comply to the + standard. + + + + + + + + Turn off all + cc's non-ANSI C + features. + + + + + Without these flags, cc will allow you to + use some of its non-standard extensions to the standard. Some + of these are very useful, but will not work with other + compilers—in fact, one of the main aims of the standard is + to allow people to write code that will work with any compiler + on any system. This is known as portable + code. + + Generally, you should try to make your code as portable as + possible, as otherwise you may have to completely re-write the + program later to get it to work somewhere else—and who + knows what you may be using in a few years time? + + + &prompt.user; cc -Wall -ansi -pedantic -o foobar foobar.c + + + + This will produce an executable foobar + after checking foobar.c for standard + compliance. + + + + + + + Specify a function library to be used during when + linking. + + The most common example of this is when compiling a + program that uses some of the mathematical functions in C. + Unlike most other platforms, these are in a separate + library from the standard C one and you have to tell the + compiler to add it. + + The rule is that if the library is called + libsomething.a, + you give cc the argument + . + For example, the math library is + libm.a, so you give + cc the argument . + A common gotcha with the math library is + that it has to be the last library on the command + line. + + + &prompt.user; cc -o foobar foobar.c -lm + + + + This will link the math library functions into + foobar. + + If you are compiling C++ code, you need to add + , or if + you are using FreeBSD 2.2 or later, to the command line + argument to link the C++ library functions. + Alternatively, you can run c++ instead + of cc, which does this for you. + c++ can also be invoked as + g++ on FreeBSD. + + + &prompt.user; cc -o foobar foobar.cc -lg++ For FreeBSD 2.1.6 and earlier &prompt.user; cc -o foobar foobar.cc -lstdc++ For FreeBSD 2.2 and later -&prompt.user; c++ -o foobar foobar.cc - +&prompt.user; c++ -o foobar foobar.cc + + -Each of these will both produce an executable -foobar from the C++ source file -foobar.cc. Note that, on Unix systems, C++ -source files traditionally end in .C, -.cxx or .cc, rather than -the MS-DOS style .cpp -(which was already used for something else). gcc -used to rely on this to work out what kind of compiler to use on the -source file; however, this restriction no longer applies, so you may -now call your C++ files .cpp with -impunity! + Each of these will both produce an executable + foobar from the C++ source file + foobar.cc. Note that, on Unix + systems, C++ source files traditionally end in + .C, .cxx or + .cc, rather than the + MS-DOS style + .cpp (which was already used for + something else). gcc used to rely on + this to work out what kind of compiler to use on the + source file; however, this restriction no longer applies, + so you may now call your C++ files + .cpp with impunity! + + + - - - - - -Common <command>cc</command> Queries and Problems + + Common <command>cc</command> Queries and Problems - - - -I am trying to write a program which uses the -sin() function and I get an error like this. -What does it mean? - - -/var/tmp/cc0143941.o: Undefined symbol `_sin' referenced from text segment - - - -When using mathematical functions like -sin(), you have to tell cc to -link in the math library, like so: - -&prompt.user; cc -o foobar foobar.c -lm - - - - - -All right, I wrote this simple program to practice using -. All it does is raise 2.1 to the power of 6. - - -#include <stdio.h> + + + + I am trying to write a program which uses the + sin() function and I get an error + like this. What does it mean? + + + /var/tmp/cc0143941.o: Undefined symbol `_sin' referenced from text segment + + + + + + When using mathematical functions like + sin(), you have to tell + cc to link in the math library, like + so: + + + &prompt.user; cc -o foobar foobar.c -lm + + + + + + + + All right, I wrote this simple program to practice + using . All it does is raise 2.1 to + the power of 6. + + + #include <stdio.h> int main() { float f; @@ -562,588 +679,707 @@ int main() { f = pow(2.1, 6); printf("2.1 ^ 6 = %f\n", f); return 0; -} - - -and I compiled it as: - - -&prompt.user; cc temp.c -lm - - -like you said I should, but I get this when I run it: - - -&prompt.user; ./a.out -2.1 ^ 6 = 1023.000000 - - -This is not the right answer! What is -going on? - - -When the compiler sees you call a function, it checks if it -has already seen a prototype for it. If it has not, it assumes the -function returns an int, which is -definitely not what you want here. - - - - -So how do I fix this? - - -The prototypes for the mathematical functions are in -math.h. If you include this file, the compiler -will be able to find the prototype and it will stop doing strange -things to your calculation! - - -#include <math.h> +} + + + + and I compiled it as: + + + &prompt.user; cc temp.c -lm + + + + like you said I should, but I get this when I run + it: + + + &prompt.user; ./a.out +2.1 ^ 6 = 1023.000000 + + + + This is not the right answer! + What is going on? + + + + When the compiler sees you call a function, it + checks if it has already seen a prototype for it. If it + has not, it assumes the function returns an + int, which is definitely not what you want + here. + + + + + + So how do I fix this? + + + + The prototypes for the mathematical functions are in + math.h. If you include this file, + the compiler will be able to find the prototype and it + will stop doing strange things to your + calculation! + + + #include <math.h> #include <stdio.h> int main() { -... - - -After recompiling it as you did before, run it: - - -&prompt.user; ./a.out -2.1 ^ 6 = 85.766121 - - -If you are using any of the mathematical functions, -always include math.h and -remember to link in the math library. - - - - -I compiled a file called foobar.c and I -cannot find an executable called foobar. Where's -it gone? - - -Remember, cc will call the executable -a.out unless you tell it differently. Use the - option: - - -&prompt.user; cc -o foobar foobar.c - - - - - -OK, I have an executable called foobar, -I can see it when I run ls, but when I type in -foobar at the command prompt it tells me there is -no such file. Why can it not find it? - - -Unlike MS-DOS, Unix does not look in the -current directory when it is trying to find out which executable you -want it to run, unless you tell it to. Either type -./foobar, which means run the file called -foobar in the current directory, or -change your PATH -environment variable so that it looks something like - - -bin:/usr/bin:/usr/local/bin:. - - -The dot at the end means look in the current directory if it is not in -any of the others. - - - - -I called my executable test, but -nothing happens when I run it. What is going on? - - -Most Unix systems have a program called -test in /usr/bin and the -shell is picking that one up before it gets to checking the current -directory. Either type: - - -&prompt.user; ./test - - -or choose a better name for your program! - - - - -I compiled my program and it seemed to run all right at -first, then there was an error and it said something about core -dumped. What does that mean? - - -The name core dump dates back to the -very early days of Unix, when the machines used core memory for -storing data. Basically, if the program failed under certain -conditions, the system would write the contents of core memory to -disk in a file called core, which the programmer -could then pore over to find out what went wrong. - - - - -Fascinating stuff, but what I am supposed to do now? - - -Use gdb to analyse the core (see ). - - - - -When my program dumped core, it said something about a -segmentation fault. What's that? - - -This basically means that your program tried to perform some sort -of illegal operation on memory; Unix is designed to protect the -operating system and other programs from rogue programs. - -Common causes for this are: - - -Trying to write to a NULL pointer, eg - -char *foo = NULL; -strcpy(foo, "bang!"); - +... + + -Using a pointer that hasn't been initialised, eg - -char *foo; -strcpy(foo, "bang!"); - -The pointer will have some random value that, with luck, -will point into an area of memory that isn't available to -your program and the kernel will kill your program before -it can do any damage. If you're unlucky, it'll point -somewhere inside your own program and corrupt one of your -data structures, causing the program to fail -mysteriously. + After recompiling it as you did before, run + it: -Trying to access past the end of an array, eg - -int bar[20]; -bar[27] = 6; + + &prompt.user; ./a.out +2.1 ^ 6 = 85.766121 + + - Trying to store something in read-only memory, eg - -char *foo = "My string"; -strcpy(foo, "bang!"); - -Unix compilers often put string literals like -"My string" into -read-only areas of memory. + If you are using any of the mathematical functions, + always include + math.h and remember to link in the + math library. + + -Doing naughty things with -malloc() and free(), eg - -char bar[80]; -free(bar); - -or - -char *foo = malloc(27); + + + I compiled a file called + foobar.c and I cannot find an + executable called foobar. Where's + it gone? + + + + Remember, cc will call the + executable a.out unless you tell it + differently. Use the + + option: + + + &prompt.user; cc -o foobar foobar.c + + + + + + + + OK, I have an executable called + foobar, I can see it when I run + ls, but when I type in + foobar at the command prompt it tells + me there is no such file. Why can it not find + it? + + + + Unlike MS-DOS, Unix does not + look in the current directory when it is trying to find + out which executable you want it to run, unless you tell + it to. Either type ./foobar, which + means run the file called + foobar in the current + directory, or change your PATH environment + variable so that it looks something like + + + bin:/usr/bin:/usr/local/bin:. + + + + The dot at the end means look in the current + directory if it is not in any of the + others. + + + + + + I called my executable test, + but nothing happens when I run it. What is going + on? + + + + Most Unix systems have a program called + test in /usr/bin + and the shell is picking that one up before it gets to + checking the current directory. Either type: + + + &prompt.user; ./test + + + + or choose a better name for your program! + + + + + + I compiled my program and it seemed to run all right + at first, then there was an error and it said something + about core dumped. What does that + mean? + + + + The name core dump dates back + to the very early days of Unix, when the machines used + core memory for storing data. Basically, if the program + failed under certain conditions, the system would write + the contents of core memory to disk in a file called + core, which the programmer could + then pore over to find out what went wrong. + + + + + + Fascinating stuff, but what I am supposed to do + now? + + + + Use gdb to analyse the core (see + ). + + + + + + When my program dumped core, it said something about + a segmentation fault. What's + that? + + + + This basically means that your program tried to + perform some sort of illegal operation on memory; Unix + is designed to protect the operating system and other + programs from rogue programs. + + Common causes for this are: + + + + Trying to write to a NULL + pointer, eg + + char *foo = NULL; +strcpy(foo, "bang!"); + + + + + Using a pointer that hasn't been initialised, + eg + + char *foo; +strcpy(foo, "bang!"); + + + The pointer will have some random value that, + with luck, will point into an area of memory that + isn't available to your program and the kernel will + kill your program before it can do any damage. If + you're unlucky, it'll point somewhere inside your + own program and corrupt one of your data structures, + causing the program to fail mysteriously. + + + + Trying to access past the end of an array, + eg + + int bar[20]; +bar[27] = 6; + + + + + Trying to store something in read-only memory, + eg + + char *foo = "My string"; +strcpy(foo, "bang!"); + + + Unix compilers often put string literals like + "My string" into read-only areas + of memory. + + + + Doing naughty things with + malloc() and + free(), eg + + char bar[80]; +free(bar); + + + or + + char *foo = malloc(27); free(foo); -free(foo); - +free(foo); + + + - + Making one of these mistakes will not always lead to + an error, but they are always bad practice. Some + systems and compilers are more tolerant than others, + which is why programs that ran well on one system can + crash when you try them on an another. + + -Making one of these mistakes will not always lead to an -error, but they are always bad practice. Some systems and -compilers are more tolerant than others, which is why programs -that ran well on one system can crash when you try them on an -another. - - - - -Sometimes when I get a core dump it says bus -error. It says in my Unix book that this means a hardware -problem, but the computer still seems to be working. Is this -true? - - -No, fortunately not (unless of course you really do have a hardware -problem…). This is usually another way of saying that you -accessed memory in a way you shouldn't have. - - - - -This dumping core business sounds as though it could be quite -useful, if I can make it happen when I want to. Can I do this, or -do I have to wait until there's an error? - - -Yes, just go to another console or xterm, do -&prompt.user; ps - -to find out the process ID of your program, and do - -&prompt.user; kill -ABRT pid - -where pid is the -process ID you looked up. - -This is useful if your program has got stuck in an infinite -loop, for instance. If your program happens to trap -SIGABRT, there are several other signals which have -a similar effect. - - - + + + Sometimes when I get a core dump it says + bus error. It says in my Unix + book that this means a hardware problem, but the + computer still seems to be working. Is this + true? + - - + + No, fortunately not (unless of course you really do + have a hardware problem…). This is usually + another way of saying that you accessed memory in a way + you shouldn't have. + + + + + This dumping core business sounds as though it could + be quite useful, if I can make it happen when I want to. + Can I do this, or do I have to wait until there's an + error? + - -Make + + Yes, just go to another console or xterm, do - -What is <command>make</command>? + &prompt.user; ps + -When you're working on a simple program with only one or two source -files, typing in - -&prompt.user; cc file1.c file2.c - -is not too bad, but it quickly becomes very tedious when there are -several files—and it can take a while to compile, too. - -One way to get around this is to use object files and only recompile -the source file if the source code has changed. So we could have -something like: - -&prompt.user; cc file1.o file2.o … file37.c &hellip - -if we'd changed file37.c, but not any of the -others, since the last time we compiled. This may speed up the -compilation quite a bit, but doesn't solve the typing -problem. + to find out the process ID of your program, and + do -Or we could write a shell script to solve the typing problem, but it -would have to re-compile everything, making it very inefficient on a -large project. - -What happens if we have hundreds of source files lying about? What if -we're working in a team with other people who forget to tell us when -they've changed one of their source files that we use? - -Perhaps we could put the two solutions together and write something -like a shell script that would contain some kind of magic rule saying -when a source file needs compiling. Now all we need now is a program -that can understand these rules, as it's a bit too complicated for the -shell. - -This program is called make. It reads in a -file, called a makefile, that tells it how -different files depend on each other, and works out which files need -to be re-compiled and which ones don't. For example, a rule could say -something like if fromboz.o is older than -fromboz.c, that means someone must have changed -fromboz.c, so it needs to be -re-compiled. The makefile also has rules telling make -how to re-compile the source file, making it a -much more powerful tool. + &prompt.user; kill -ABRT pid + -Makefiles are typically kept in the same directory as the -source they apply to, and can be called -makefile, Makefile or -MAKEFILE. Most programmers use the name -Makefile, as this puts it near the top of a -directory listing, where it can easily be seen.They -don't use the MAKEFILE form as block capitals -are often used for documentation files like -README. - - + where + pid is + the process ID you looked up. - -Example of using <command>make</command> + This is useful if your program has got stuck in an + infinite loop, for instance. If your program happens to + trap SIGABRT, there are several other + signals which have a similar effect. + + + + + -Here's a very simple make file: - -foo: foo.c - cc -o foo foo.c - -It consists of two lines, a dependency line and a creation line. - -The dependency line here consists of the name of the program -(known as the target), followed by a colon, -then whitespace, then the name of the source file. When -make reads this line, it looks to see if -foo exists; if it exists, it compares the time -foo was last modified to the time -foo.c was last modified. If -foo does not exist, or is older than -foo.c, it then looks at the creation line to -find out what to do. In other words, this is the rule for working out -when foo.c needs to be re-compiled. + + Make -The creation line starts with a tab (press the -tab key) and then the command you would type to -create foo if you were doing it at a command -prompt. If foo is out of date, or does not -exist, make then executes this command to create -it. In other words, this is the rule which tells make how to -re-compile foo.c. + + What is <command>make</command>? -So, when you type make, it will make -sure that foo is up to date with respect to your -latest changes to foo.c. This principle can be -extended to Makefiles with hundreds of -targets—in fact, on FreeBSD, it is possible to compile the -entire operating system just by typing make -world in the appropriate directory! + When you're working on a simple program with only one or + two source files, typing in -Another useful property of makefiles is that the targets don't have -to be programs. For instance, we could have a make file that looks -like this: - -foo: foo.c + &prompt.user; cc file1.c file2.c + + + is not too bad, but it quickly becomes very tedious when + there are several files—and it can take a while to + compile, too. + + One way to get around this is to use object files and only + recompile the source file if the source code has changed. So + we could have something like: + + &prompt.user; cc file1.o file2.o … file37.c &hellip + + + if we'd changed file37.c, but not any + of the others, since the last time we compiled. This may + speed up the compilation quite a bit, but doesn't solve the + typing problem. + + Or we could write a shell script to solve the typing + problem, but it would have to re-compile everything, making it + very inefficient on a large project. + + What happens if we have hundreds of source files lying + about? What if we're working in a team with other people who + forget to tell us when they've changed one of their source + files that we use? + + Perhaps we could put the two solutions together and write + something like a shell script that would contain some kind of + magic rule saying when a source file needs compiling. Now all + we need now is a program that can understand these rules, as + it's a bit too complicated for the shell. + + This program is called make. It reads + in a file, called a makefile, that + tells it how different files depend on each other, and works + out which files need to be re-compiled and which ones don't. + For example, a rule could say something like if + fromboz.o is older than + fromboz.c, that means someone must have + changed fromboz.c, so it needs to be + re-compiled. The makefile also has rules telling + make how to re-compile the source file, + making it a much more powerful tool. + + Makefiles are typically kept in the same directory as the + source they apply to, and can be called + makefile, Makefile + or MAKEFILE. Most programmers use the + name Makefile, as this puts it near the + top of a directory listing, where it can easily be + seen. + + + They don't use the MAKEFILE form + as block capitals are often used for documentation files + like README. + + + + + Example of using <command>make</command> + + Here's a very simple make file: + + foo: foo.c + cc -o foo foo.c + + + It consists of two lines, a dependency line and a creation + line. + + The dependency line here consists of the name of the + program (known as the target), followed + by a colon, then whitespace, then the name of the source file. + When make reads this line, it looks to see + if foo exists; if it exists, it compares + the time foo was last modified to the + time foo.c was last modified. If + foo does not exist, or is older than + foo.c, it then looks at the creation line + to find out what to do. In other words, this is the rule for + working out when foo.c needs to be + re-compiled. + + The creation line starts with a tab (press + the tab key) and then the command you would + type to create foo if you were doing it + at a command prompt. If foo is out of + date, or does not exist, make then executes + this command to create it. In other words, this is the rule + which tells make how to re-compile + foo.c. + + So, when you type make, it will + make sure that foo is up to date with + respect to your latest changes to foo.c. + This principle can be extended to + Makefiles with hundreds of + targets—in fact, on FreeBSD, it is possible to compile + the entire operating system just by typing make + world in the appropriate directory! + + Another useful property of makefiles is that the targets + don't have to be programs. For instance, we could have a make + file that looks like this: + + foo: foo.c cc -o foo foo.c install: - cp foo /home/me - -We can tell make which target we want to make by typing: - -&prompt.user; make target - -make will then only look at that target and ignore any -others. For example, if we type make foo with the -makefile above, make will ignore the install target. - -If we just type make on its own, make -will always look at the first target and then stop without looking at -any others. So if we typed make here, it will -just go to the foo target, re-compile -foo if necessary, and then stop without going on -to the install target. + cp foo /home/me + -Notice that the install target doesn't -actually depend on anything! This means that the command on the -following line is always executed when we try to make that target by -typing make install. In this case, it will -copy foo into the user's home directory. This is -often used by application makefiles, so that the application can be -installed in the correct directory when it has been correctly -compiled. + We can tell make which target we want to make by + typing: -This is a slightly confusing subject to try and explain. If you -don't quite understand how make works, the best -thing to do is to write a simple program like hello -world and a make file like the one above and experiment. Then -progress to using more than one source file, or having the source -file include a header file. The touch command is -very useful here—it changes the date on a file without you -having to edit it. - - + &prompt.user; make target + - -FreeBSD Makefiles + make will then only look at that target + and ignore any others. For example, if we type + make foo with the makefile above, make + will ignore the install target. -Makefiles can be rather complicated to write. Fortunately, -BSD-based systems like FreeBSD come with some very powerful ones as -part of the system. One very good example of this is the FreeBSD -ports system. Here's the essential part of a typical ports -Makefile: -MASTER_SITES= ftp://freefall.cdrom.com/pub/FreeBSD/LOCAL_PORTS/ + If we just type make on its own, + make will always look at the first target and then stop + without looking at any others. So if we typed + make here, it will just go to the + foo target, re-compile + foo if necessary, and then stop without + going on to the install target. + + Notice that the install target doesn't + actually depend on anything! This means that the command on + the following line is always executed when we try to make that + target by typing make install. In this + case, it will copy foo into the user's + home directory. This is often used by application makefiles, + so that the application can be installed in the correct + directory when it has been correctly compiled. + + This is a slightly confusing subject to try and explain. + If you don't quite understand how make + works, the best thing to do is to write a simple program like + hello world and a make file like the one above + and experiment. Then progress to using more than one source + file, or having the source file include a header file. The + touch command is very useful here—it + changes the date on a file without you having to edit + it. + + + + FreeBSD Makefiles + + Makefiles can be rather complicated to write. Fortunately, + BSD-based systems like FreeBSD come with some very powerful + ones as part of the system. One very good example of this is + the FreeBSD ports system. Here's the essential part of a + typical ports Makefile: + + MASTER_SITES= ftp://freefall.cdrom.com/pub/FreeBSD/LOCAL_PORTS/ DISTFILES= scheme-microcode+dist-7.3-freebsd.tgz -.include <bsd.port.mk> - -Now, if we go to the directory for this port and type -make, the following happens: +.include <bsd.port.mk> + - -A check is made to see if the source code for this port is -already on the system. + Now, if we go to the directory for this port and type + make, the following happens: -If it isn't, an FTP connection to the URL in -MASTER_SITES is set up to download the -source. + + + A check is made to see if the source code for this + port is already on the system. + -The checksum for the source is calculated and compared it with -one for a known, good, copy of the source. This is to make sure that -the source was not corrupted while in transit. + + If it isn't, an FTP connection to the URL in + MASTER_SITES is set up to download the + source. + -Any changes required to make the source work on FreeBSD are -applied—this is known as patching. + + The checksum for the source is calculated and compared + it with one for a known, good, copy of the source. This + is to make sure that the source was not corrupted while in + transit. + -Any special configuration needed for the source is done. -(Many Unix program distributions try to work out which version of -Unix they are being compiled on and which optional Unix features are -present—this is where they are given the information in the -FreeBSD ports scenario). + + Any changes required to make the source work on + FreeBSD are applied—this is known as + patching. + -The source code for the program is compiled. In effect, -we change to the directory where the source was unpacked and do -make—the program's own make file has the -necessary information to build the program. + + Any special configuration needed for the source is + done. (Many Unix program distributions try to work out + which version of Unix they are being compiled on and which + optional Unix features are present—this is where + they are given the information in the FreeBSD ports + scenario). + -We now have a compiled version of the program. If we -wish, we can test it now; when we feel confident about the program, -we can type make install. This will cause the -program and any supporting files it needs to be copied into the -correct location; an entry is also made into a package -database, so that the port can easily be uninstalled later -if we change our mind about it. + + The source code for the program is compiled. In + effect, we change to the directory where the source was + unpacked and do make—the + program's own make file has the necessary information to + build the program. + - - -Now I think you'll agree that's rather impressive for a four -line script! + + We now have a compiled version of the program. If we + wish, we can test it now; when we feel confident about the + program, we can type make install. + This will cause the program and any supporting files it + needs to be copied into the correct location; an entry is + also made into a package database, so + that the port can easily be uninstalled later if we change + our mind about it. + + -The secret lies in the last line, which tells -make to look in the system makefile called -bsd.port.mk. It's easy to overlook this line, -but this is where all the clever stuff comes from—someone has -written a makefile that tells make to do all the -things above (plus a couple of other things I didn't mention, -including handling any errors that may occur) and anyone can get -access to that just by putting a single line in their own make -file! + Now I think you'll agree that's rather impressive for a + four line script! -If you want to have a look at these system makefiles, they're -in /usr/share/mk, but it's probably best to wait -until you've had a bit of practice with makefiles, as they are very -complicated (and if you do look at them, make sure you have a flask -of strong coffee handy!) + The secret lies in the last line, which tells + make to look in the system makefile called + bsd.port.mk. It's easy to overlook this + line, but this is where all the clever stuff comes + from—someone has written a makefile that tells + make to do all the things above (plus a + couple of other things I didn't mention, including handling + any errors that may occur) and anyone can get access to that + just by putting a single line in their own make file! - + If you want to have a look at these system makefiles, + they're in /usr/share/mk, but it's + probably best to wait until you've had a bit of practice with + makefiles, as they are very complicated (and if you do look at + them, make sure you have a flask of strong coffee + handy!) + - -More advanced uses of <command>make</command> + + More advanced uses of <command>make</command> -Make is a very powerful tool, and can do much -more than the simple example above shows. Unfortunately, there are -several different versions of make, and they all -differ considerably. The best way to learn what they can do is -probably to read the documentation—hopefully this introduction will -have given you a base from which you can do this. + Make is a very powerful tool, and can + do much more than the simple example above shows. + Unfortunately, there are several different versions of + make, and they all differ considerably. + The best way to learn what they can do is probably to read the + documentation—hopefully this introduction will have + given you a base from which you can do this. -The version of make that comes with FreeBSD is the Berkeley -make; there is a tutorial for it in -/usr/share/doc/psd/12.make. To view it, do - -&prompt.user; zmore paper.ascii.gz - -in that directory. - -Many applications in the ports use GNU -make, which has a very good set of info -pages. If you have installed any of these ports, GNU -make will automatically have been installed as -gmake. It's also available as a port and package -in its own right. + The version of make that comes with FreeBSD is the + Berkeley make; there is a tutorial + for it in /usr/share/doc/psd/12.make. To + view it, do -To view the info pages for GNU make, -you will have to edit the dir file in the -/usr/local/info directory to add an entry for -it. This involves adding a line like - - * Make: (make). The GNU Make utility. - -to the file. Once you have done this, you can type -info and then select -make from the menu (or in -Emacs, do C-h -i). + &prompt.user; zmore paper.ascii.gz + - - + in that directory. - -Debugging + Many applications in the ports use GNU + make, which has a very good set of + info pages. If you have installed any of these + ports, GNU make will automatically + have been installed as gmake. It's also + available as a port and package in its own right. - -The Debugger + To view the info pages for GNU + make, you will have to edit the + dir file in the + /usr/local/info directory to add an entry + for it. This involves adding a line like -The debugger that comes with FreeBSD is called -gdb (GNU -debugger). You start it up by typing - -&prompt.user; gdb progname - -although most people prefer to run it inside -Emacs. You can do this by: - -M-x gdb RET progname RET - -Using a debugger allows you to run the program under more -controlled circumstances. Typically, you can step through the program -a line at a time, inspect the value of variables, change them, tell -the debugger to run up to a certain point and then stop, and so on. -You can even attach to a program that's already running, or load a -core file to investigate why the program crashed. It's even possible -to debug the kernel, though that's a little trickier than the user -applications we'll be discussing in this section. + * Make: (make). The GNU Make utility. + -gdb has quite good on-line help, as well as -a set of info pages, so this section will concentrate on a few of the -basic commands. + to the file. Once you have done this, you can type + info and then select + make from the menu (or in + Emacs, do C-h + i). + + -Finally, if you find its text-based command-prompt style -off-putting, there's a graphical front-end for it xxgdb -in the ports collection. + + Debugging -This section is intended to be an introduction to using -gdb and does not cover specialised topics such as -debugging the kernel. - - + + The Debugger - -Running a program in the debugger + The debugger that comes with FreeBSD is called + gdb (GNU + debugger). You start it up by typing -You'll need to have compiled the program with the - option to get the most out of using -gdb. It will work without, but you'll only see the -name of the function you're in, instead of the source code. If you -see a line like: - -… (no debugging symbols found) …when -gdb starts up, you'll know that the program wasn't -compiled with the option. - -At the gdb prompt, type break -main. This will tell the debugger to skip over the -preliminary set-up code in the program and start at the beginning of -your code. Now type run to start the -program—it will start at the beginning of the set-up code and -then get stopped by the debugger when it calls -main(). (If you've ever wondered where -main() gets called from, now you know!). + &prompt.user; gdb progname + -You can now step through the program, a line at a time, by -pressing n. If you get to a function call, you can -step into it by pressing s. Once you're in a -function call, you can return from stepping into a function call by -pressing f. You can also use up and -down to take a quick look at the caller. + although most people prefer to run it inside + Emacs. You can do this by: -Here's a simple example of how to spot a mistake in a program -with gdb. This is our program (with a deliberate -mistake): - -#include <stdio.h> + M-x gdb RET progname RET + + + Using a debugger allows you to run the program under more + controlled circumstances. Typically, you can step through the + program a line at a time, inspect the value of variables, + change them, tell the debugger to run up to a certain point + and then stop, and so on. You can even attach to a program + that's already running, or load a core file to investigate why + the program crashed. It's even possible to debug the kernel, + though that's a little trickier than the user applications + we'll be discussing in this section. + + gdb has quite good on-line help, as + well as a set of info pages, so this section will concentrate + on a few of the basic commands. + + Finally, if you find its text-based command-prompt style + off-putting, there's a graphical front-end for it xxgdb in the ports + collection. + + This section is intended to be an introduction to using + gdb and does not cover specialised topics + such as debugging the kernel. + + + + Running a program in the debugger + + You'll need to have compiled the program with the + option to get the most out of using + gdb. It will work without, but you'll only + see the name of the function you're in, instead of the source + code. If you see a line like: + + … (no debugging symbols found) … + + + when gdb starts up, you'll know that + the program wasn't compiled with the + option. + + At the gdb prompt, type + break main. This will tell the + debugger to skip over the preliminary set-up code in the + program and start at the beginning of your code. Now type + run to start the program—it will + start at the beginning of the set-up code and then get stopped + by the debugger when it calls main(). + (If you've ever wondered where main() + gets called from, now you know!). + + You can now step through the program, a line at a time, by + pressing n. If you get to a function call, + you can step into it by pressing s. Once + you're in a function call, you can return from stepping into a + function call by pressing f. You can also + use up and down to take + a quick look at the caller. + + Here's a simple example of how to spot a mistake in a + program with gdb. This is our program + (with a deliberate mistake): + + #include <stdio.h> int bazz(int anint); @@ -1158,21 +1394,26 @@ main() { int bazz(int anint) { printf("You gave me %d\n", anint); return anint; -} - -This program sets i to be 5 -and passes it to a function bazz() which prints -out the number we gave it. +} + -When we compile and run the program we get - -&prompt.user; cc -g -o temp temp.c + This program sets i to be + 5 and passes it to a function + bazz() which prints out the number we + gave it. + + When we compile and run the program we get + + &prompt.user; cc -g -o temp temp.c &prompt.user; ./temp This is my program -anint = 4231 - -That wasn't what we expected! Time to see what's going -on!&prompt.user; gdb temp +anint = 4231 + + + That wasn't what we expected! Time to see what's going + on! + + &prompt.user; gdb temp GDB is free software and you are welcome to distribute copies of it under certain conditions; type "show copying" to see the conditions. There is absolutely no warranty for GDB; type "show warranty" for details. @@ -1187,71 +1428,78 @@ Breakpoint 1, main () at temp.c:9 gdb stops This is my program Program prints out (gdb) s step into bazz() bazz (anint=4231) at temp.c:17 gdb displays stack frame -(gdb) +(gdb) + - -Hang on a minute! How did anint get to be -4231? Didn't we set it to be 5 -in main()? Let's move up to -main() and have a look. + Hang on a minute! How did anint get to be + 4231? Didn't we set it to be + 5 in main()? Let's + move up to main() and have a look. -(gdb) up Move up call stack + (gdb) up Move up call stack #1 0x1625 in main () at temp.c:11 gdb displays stack frame (gdb) p i Show us the value of i $1 = 4231 gdb displays 4231 - - -Oh dear! Looking at the code, we forgot to initialise -i. We meant to put - -… + + + Oh dear! Looking at the code, we forgot to initialise + i. We meant to put + + … main() { int i; i = 5; printf("This is my program\n"); -&hellip - -but we left the i=5; line out. As we didn't -initialise i, it had whatever number happened to be -in that area of memory when the program ran, which in this case -happened to be 4231. +&hellip + -gdb displays the stack frame -every time we go into or out of a function, even if we're using -up and down to move around the -call stack. This shows the name of the function and the values of -its arguments, which helps us keep track of where we are and what's -going on. (The stack is a storage area where the program stores -information about the arguments passed to functions and where to go -when it returns from a function call). + but we left the i=5; line out. As we + didn't initialise i, it had whatever number + happened to be in that area of memory when the program ran, + which in this case happened to be + 4231. - + + gdb displays the stack frame every + time we go into or out of a function, even if we're using + up and down to move + around the call stack. This shows the name of the function + and the values of its arguments, which helps us keep track + of where we are and what's going on. (The stack is a + storage area where the program stores information about the + arguments passed to functions and where to go when it + returns from a function call). + + - -Examining a core file + + Examining a core file -A core file is basically a file which contains the complete -state of the process when it crashed. In the good old -days, programmers had to print out hex listings of core files -and sweat over machine code manuals, but now life is a bit easier. -Incidentally, under FreeBSD and other 4.4BSD systems, a core file is -called progname.core instead of just -core, to make it clearer which program a core -file belongs to. + A core file is basically a file which contains the + complete state of the process when it crashed. In the + good old days, programmers had to print out hex + listings of core files and sweat over machine code manuals, + but now life is a bit easier. Incidentally, under FreeBSD and + other 4.4BSD systems, a core file is called + progname.core instead of just + core, to make it clearer which program a + core file belongs to. -To examine a core file, start up gdb in the -usual way. Instead of typing break or -run, type - -(gdb) core progname.core - -If you're not in the same directory as the core file, you'll have to -do dir /path/to/core/file first. - -You should see something like this: - -&prompt.user; gdb a.out + To examine a core file, start up gdb in + the usual way. Instead of typing break or + run, type + + (gdb) core progname.core + + + If you're not in the same directory as the core file, + you'll have to do dir + /path/to/core/file first. + + You should see something like this: + + &prompt.user; gdb a.out GDB is free software and you are welcome to distribute copies of it under certain conditions; type "show copying" to see the conditions. There is absolutely no warranty for GDB; type "show warranty" for details. @@ -1261,52 +1509,60 @@ Core was generated by `a.out'. Program terminated with signal 11, Segmentation fault. Cannot access memory at address 0x7020796d. #0 0x164a in bazz (anint=0x5) at temp.c:17 -(gdb) - -In this case, the program was called -a.out, so the core file is called -a.out.core. We can see that the program crashed -due to trying to access an area in memory that was not available to -it in a function called bazz. +(gdb) + -Sometimes it's useful to be able to see how a function was -called, as the problem could have occurred a long way up the call -stack in a complex program. The bt command causes -gdb to print out a back-trace of the call -stack: - -(gdb) bt + In this case, the program was called + a.out, so the core file is called + a.out.core. We can see that the program + crashed due to trying to access an area in memory that was not + available to it in a function called + bazz. + + Sometimes it's useful to be able to see how a function was + called, as the problem could have occurred a long way up the + call stack in a complex program. The bt + command causes gdb to print out a + back-trace of the call stack: + + (gdb) bt #0 0x164a in bazz (anint=0x5) at temp.c:17 #1 0xefbfd888 in end () #2 0x162c in main () at temp.c:11 -(gdb)The end() function is called when -a program crashes; in this case, the bazz() -function was called from main(). +(gdb) + - + The end() function is called when a + program crashes; in this case, the bazz() + function was called from main(). + - -Attaching to a running program + + Attaching to a running program -One of the neatest features about gdb is -that it can attach to a program that's already running. Of course, -that assumes you have sufficient permissions to do so. A common -problem is when you are stepping through a program that forks, and -you want to trace the child, but the debugger will only let you trace -the parent. + One of the neatest features about gdb + is that it can attach to a program that's already running. Of + course, that assumes you have sufficient permissions to do so. + A common problem is when you are stepping through a program + that forks, and you want to trace the child, but the debugger + will only let you trace the parent. -What you do is start up another gdb, use -ps to find the process ID for the child, and -do(gdb) attach pid - -in gdb, and then debug as usual. - -That's all very well, you're probably thinking, -but by the time I've done that, the child process will be over -the hill and far away. Fear not, gentle reader, here's how to -do it (courtesy of the gdb info pages): - -&hellip + What you do is start up another gdb, + use ps to find the process ID for the + child, and do + + (gdb) attach pid + + + in gdb, and then debug as usual. + + That's all very well, you're probably + thinking, but by the time I've done that, the child + process will be over the hill and far away. Fear + not, gentle reader, here's how to do it (courtesy of the + gdb info pages): + + &hellip if ((pid = fork()) < 0) /* _Always_ check this */ error(); else if (pid == 0) { /* child */ @@ -1316,223 +1572,275 @@ else if (pid == 0) { /* child */ sleep(10); /* Wait until someone attaches to us */ &hellip } else { /* parent */ - &hellip - -Now all you have to do is attach to the child, set -PauseMode to 0, and -wait for the sleep() call to return! - - - + &hellip + - -Using Emacs as a Development Environment + Now all you have to do is attach to the child, set + PauseMode to 0, and wait + for the sleep() call to return! + + - -Emacs + + Using Emacs as a Development Environment -Unfortunately, Unix systems don't come with the kind of -everything-you-ever-wanted-and-lots-more-you-didn't-in-one-gigantic-package -integrated development environments that other systems -have.At least, not unless you pay out very large sums -of money. However, it is possible to set up your -own environment. It may not be as pretty, and it may not be quite as -integrated, but you can set it up the way you want it. And it's free. -And you have the source to it. + + Emacs -The key to it all is Emacs. Now there are some people who -loathe it, but many who love it. If you're one of the former, I'm -afraid this section will hold little of interest to you. Also, you'll -need a fair amount of memory to run it—I'd recommend 8MB in -text mode and 16MB in X as the bare minimum to get reasonable -performance. + Unfortunately, Unix systems don't come with the kind of + everything-you-ever-wanted-and-lots-more-you-didn't-in-one-gigantic-package + integrated development environments that other systems + have. -Emacs is basically a highly customisable editor—indeed, -it has been customised to the point where it's more like an operating -system than an editor! Many developers and sysadmins do in fact -spend practically all their time working inside Emacs, leaving it -only to log out. + + At least, not unless you pay out very large sums of + money. + -It's impossible even to summarise everything Emacs can do here, but -here are some of the features of interest to developers: - - + However, it is possible to set up your own environment. It + may not be as pretty, and it may not be quite as integrated, + but you can set it up the way you want it. And it's free. + And you have the source to it. -Very powerful editor, allowing search-and-replace on -both strings and regular expressions (patterns), jumping to start/end -of block expression, etc, etc. + The key to it all is Emacs. Now there are some people who + loathe it, but many who love it. If you're one of the former, + I'm afraid this section will hold little of interest to you. + Also, you'll need a fair amount of memory to run it—I'd + recommend 8MB in text mode and 16MB in X as the bare minimum + to get reasonable performance. -Pull-down menus and online help. + Emacs is basically a highly customisable + editor—indeed, it has been customised to the point where + it's more like an operating system than an editor! Many + developers and sysadmins do in fact spend practically all + their time working inside Emacs, leaving it only to log + out. -Language-dependent syntax highlighting and -indentation. + It's impossible even to summarise everything Emacs can do + here, but here are some of the features of interest to + developers: -Completely customisable. + + + Very powerful editor, allowing search-and-replace on + both strings and regular expressions (patterns), jumping + to start/end of block expression, etc, etc. + -You can compile and debug programs within -Emacs. + + Pull-down menus and online help. + -On a compilation error, you can jump to the offending -line of source code. + + Language-dependent syntax highlighting and + indentation. + -Friendly-ish front-end to the info -program used for reading GNU hypertext documentation, including the -documentation on Emacs itself. + + Completely customisable. + -Friendly front-end to gdb, -allowing you to look at the source code as you step through your -program. + + You can compile and debug programs within + Emacs. + -You can read Usenet news and mail while your program -is compiling. + + On a compilation error, you can jump to the offending + line of source code. + -And doubtless many more that I've overlooked. + + Friendly-ish front-end to the info + program used for reading GNU hypertext documentation, + including the documentation on Emacs itself. + -Emacs can be installed on FreeBSD using the Emacs -port. + + Friendly front-end to gdb, allowing + you to look at the source code as you step through your + program. + -Once it's installed, start it up and do C-h -t to read an Emacs tutorial—that means hold down -the control key, press h, let go of -the control key, and then press t. -(Alternatively, you can you use the mouse to select Emacs -Tutorial from the Help menu). + + You can read Usenet news and mail while your program + is compiling. + + -Although Emacs does have menus, it's well worth learning the -key bindings, as it's much quicker when you're editing something to -press a couple of keys than to try and find the mouse and then click -on the right place. And, when you're talking to seasoned Emacs users, -you'll find they often casually throw around expressions like -M-x replace-s RET foo RET bar RET -so it's useful to know what they mean. And in any case, Emacs has far -too many useful functions for them to all fit on the menu -bars. + And doubtless many more that I've overlooked. -Fortunately, it's quite easy to pick up the key-bindings, as -they're displayed next to the menu item. My advice is to use the -menu item for, say, opening a file until you understand how it works -and feel confident with it, then try doing C-x C-f. When you're happy -with that, move on to another menu command. + Emacs can be installed on FreeBSD using the Emacs + port. -If you can't remember what a particular combination of keys -does, select Describe Key from the -Help menu and type it in—Emacs will tell you -what it does. You can also use the Command -Apropos menu item to find out all the commands which -contain a particular word in them, with the key binding next to -it. + Once it's installed, start it up and do C-h + t to read an Emacs tutorial—that means + hold down the control key, press + h, let go of the control + key, and then press t. (Alternatively, you + can you use the mouse to select Emacs + Tutorial from the Help + menu). -By the way, the expression above means hold down the -Meta key, press x, release the -Meta key, type replace-s -(short for replace-string—another feature of -Emacs is that you can abbreviate commands), press the -return key, type foo (the -string you want replaced), press the return key, -type bar (the string you want to replace foo with) -and press return again. Emacs will then do the -search-and-replace operation you've just requested. + Although Emacs does have menus, it's well worth learning + the key bindings, as it's much quicker when you're editing + something to press a couple of keys than to try and find the + mouse and then click on the right place. And, when you're + talking to seasoned Emacs users, you'll find they often + casually throw around expressions like M-x + replace-s RET foo RET bar RET so it's + useful to know what they mean. And in any case, Emacs has far + too many useful functions for them to all fit on the menu + bars. -If you're wondering what on earth the Meta key -is, it's a special key that many Unix workstations have. -Unfortunately, PC's don't have one, so it's usually the -alt key (or if you're unlucky, the escape -key). + Fortunately, it's quite easy to pick up the key-bindings, + as they're displayed next to the menu item. My advice is to + use the menu item for, say, opening a file until you + understand how it works and feel confident with it, then try + doing C-x C-f. When you're happy with that, move on to + another menu command. -Oh, and to get out of Emacs, do C-x C-c -(that means hold down the control key, press -x, press c and release the -control key). If you have any unsaved files open, -Emacs will ask you if you want to save them. (Ignore the bit in the -documentation where it says C-z is the usual way -to leave Emacs—that leaves Emacs hanging around in the -background, and is only really useful if you're on a system which -doesn't have virtual terminals). + If you can't remember what a particular combination of + keys does, select Describe Key from + the Help menu and type it in—Emacs + will tell you what it does. You can also use the + Command Apropos menu item to find + out all the commands which contain a particular word in them, + with the key binding next to it. - + By the way, the expression above means hold down the + Meta key, press x, release + the Meta key, type + replace-s (short for + replace-string—another feature of + Emacs is that you can abbreviate commands), press the + return key, type foo + (the string you want replaced), press the + return key, type bar (the string you want to + replace foo with) and press + return again. Emacs will then do the + search-and-replace operation you've just requested. - -Configuring Emacs + If you're wondering what on earth the + Meta key is, it's a special key that many + Unix workstations have. Unfortunately, PC's don't have one, + so it's usually the alt key (or if you're + unlucky, the escape key). -Emacs does many wonderful things; some of them are built in, -some of them need to be configured. + Oh, and to get out of Emacs, do C-x C-c + (that means hold down the control key, press + x, press c and release the + control key). If you have any unsaved files + open, Emacs will ask you if you want to save them. (Ignore + the bit in the documentation where it says + C-z is the usual way to leave + Emacs—that leaves Emacs hanging around in the + background, and is only really useful if you're on a system + which doesn't have virtual terminals). + -Instead of using a proprietary macro language for -configuration, Emacs uses a version of Lisp specially adapted for -editors, known as Emacs Lisp. This can be quite useful if you want to -go on and learn something like Common Lisp, as it's considerably -smaller than Common Lisp (although still quite big!). + + Configuring Emacs -The best way to learn Emacs Lisp is to download the Emacs -Tutorial + Emacs does many wonderful things; some of them are built + in, some of them need to be configured. -However, there's no need to actually know any Lisp to get -started with configuring Emacs, as I've included a sample -.emacs file, which should be enough to get you -started. Just copy it into your home directory and restart Emacs if -it's already running; it will read the commands from the file and -(hopefully) give you a useful basic setup. + Instead of using a proprietary macro language for + configuration, Emacs uses a version of Lisp specially adapted + for editors, known as Emacs Lisp. This can be quite useful if + you want to go on and learn something like Common Lisp, as + it's considerably smaller than Common Lisp (although still + quite big!). - + The best way to learn Emacs Lisp is to download the Emacs + Tutorial - -A sample <filename>.emacs</filename> file + However, there's no need to actually know any Lisp to get + started with configuring Emacs, as I've included a sample + .emacs file, which should be enough to + get you started. Just copy it into your home directory and + restart Emacs if it's already running; it will read the + commands from the file and (hopefully) give you a useful basic + setup. + -Unfortunately, there's far too much here to explain it in detail; -however there are one or two points worth mentioning. - - + + A sample <filename>.emacs</filename> file -Everything beginning with a ; is a -comment and is ignored by Emacs. + Unfortunately, there's far too much here to explain it in + detail; however there are one or two points worth + mentioning. -In the first line, the --*- Emacs-Lisp -*- is so that we can -edit the .emacs file itself within Emacs and get -all the fancy features for editing Emacs Lisp. Emacs usually tries to -guess this based on the filename, and may not get it right for -.emacs. + + + Everything beginning with a ; is a comment + and is ignored by Emacs. + -The tab key is bound to an -indentation function in some modes, so when you press the tab key, it -will indent the current line of code. If you want to put a -tab character in whatever you're writing, hold the -control key down while you're pressing the -tab key. + + In the first line, the + -*- Emacs-Lisp -*- is so that + we can edit the .emacs file itself + within Emacs and get all the fancy features for editing + Emacs Lisp. Emacs usually tries to guess this based on + the filename, and may not get it right for + .emacs. + -This file supports syntax highlighting for C, C++, -Perl, Lisp and Scheme, by guessing the language from the -filename. + + The tab key is bound to an + indentation function in some modes, so when you press the + tab key, it will indent the current line of code. If you + want to put a tab character in whatever + you're writing, hold the control key down + while you're pressing the tab key. + -Emacs already has a pre-defined function called -next-error. In a compilation output window, this -allows you to move from one compilation error to the next by doing -M-n; we define a complementary function, -previous-error, that allows you to go to a -previous error by doing M-p. The nicest feature of -all is that C-c C-c will open up the source file -in which the error occurred and jump to the appropriate -line. + + This file supports syntax highlighting for C, C++, + Perl, Lisp and Scheme, by guessing the language from the + filename. + - We enable Emacs's ability to act as a server, so -that if you're doing something outside Emacs and you want to edit a -file, you can just type in - -&prompt.user; emacsclient filename - -and then you can edit the file in your Emacs!Many -Emacs users set their EDITOR environment to -emacsclient so this happens every time they need -to edit a file. + + Emacs already has a pre-defined function called + next-error. In a compilation output + window, this allows you to move from one compilation error + to the next by doing M-n; we define a + complementary function, + previous-error, that allows you to go + to a previous error by doing M-p. The + nicest feature of all is that C-c C-c + will open up the source file in which the error occurred + and jump to the appropriate line. + - - - -A sample <filename>.emacs</filename> file -;; -*-Emacs-Lisp-*- + + We enable Emacs's ability to act as a server, so that + if you're doing something outside Emacs and you want to + edit a file, you can just type in + + &prompt.user; emacsclient filename + + + and then you can edit the file in your + Emacs! + + + Many Emacs users set their EDITOR environment to + emacsclient so this happens every + time they need to edit a file. + + + + + + A sample <filename>.emacs</filename> file + + ;; -*-Emacs-Lisp-*- ;; This file is designed to be re-evaled; use the variable first-time ;; to avoid any problems with this. @@ -1813,127 +2121,148 @@ in font-lock-auto-mode-list" ;; All done (message "All done, %s%s" (user-login-name) ".") - - - - + + + - -Extending the Range of Languages Emacs Understands + + Extending the Range of Languages Emacs Understands -Now, this is all very well if you only want to program in the -languages already catered for in the .emacs file -(C, C++, Perl, Lisp and Scheme), but what happens if a new language -called whizbang comes out, full of exciting -features? + Now, this is all very well if you only want to program in + the languages already catered for in the + .emacs file (C, C++, Perl, Lisp and + Scheme), but what happens if a new language called + whizbang comes out, full of exciting + features? -The first thing to do is find out if whizbang -comes with any files that tell Emacs about the language. These -usually end in .el, short for Emacs -Lisp. For example, if whizbang is a FreeBSD -port, we can locate these files by doing - -&prompt.user; find /usr/ports/lang/whizbang -name "*.el" -print - -and install them by copying them into the Emacs site Lisp directory. On -FreeBSD 2.1.0-RELEASE, this is -/usr/local/share/emacs/site-lisp. + The first thing to do is find out if whizbang comes with + any files that tell Emacs about the language. These usually + end in .el, short for Emacs + Lisp. For example, if whizbang is a FreeBSD port, we + can locate these files by doing -So for example, if the output from the find command was - -/usr/ports/lang/whizbang/work/misc/whizbang.el - -we would do - -&prompt.root; cp /usr/ports/lang/whizbang/work/misc/whizbang.el /usr/local/share/emacs/site-lisp - -Next, we need to decide what extension whizbang source files -have. Let's say for the sake of argument that they all end in -.wiz. We need to add an entry to our -.emacs file to make sure Emacs will be able to -use the information in whizbang.el. + &prompt.user; find /usr/ports/lang/whizbang -name "*.el" -print + -Find the auto-mode-alist entry in -.emacs and add a line for whizbang, such -as: - -… + and install them by copying them into the Emacs site Lisp + directory. On FreeBSD 2.1.0-RELEASE, this is + /usr/local/share/emacs/site-lisp. + + So for example, if the output from the find command + was + + /usr/ports/lang/whizbang/work/misc/whizbang.el + + + we would do + + &prompt.root; cp /usr/ports/lang/whizbang/work/misc/whizbang.el /usr/local/share/emacs/site-lisp + + + Next, we need to decide what extension whizbang source + files have. Let's say for the sake of argument that they all + end in .wiz. We need to add an entry to + our .emacs file to make sure Emacs will + be able to use the information in + whizbang.el. + + Find the auto-mode-alist entry in + .emacs and add a line for whizbang, such + as: + + … ("\\.lsp$" . lisp-mode) ("\\.wiz$" . whizbang-mode) ("\\.scm$" . scheme-mode) -… - -This means that Emacs will automatically go into -whizbang-mode when you edit a file ending in -.wiz. +… + -Just below this, you'll find the -font-lock-auto-mode-list entry. Add -whizbang-mode to it like so: - -;; Auto font lock mode + This means that Emacs will automatically go into + whizbang-mode when you edit a file ending + in .wiz. + + Just below this, you'll find the + font-lock-auto-mode-list entry. Add + whizbang-mode to it like so: + + ;; Auto font lock mode (defvar font-lock-auto-mode-list (list 'c-mode 'c++-mode 'c++-c-mode 'emacs-lisp-mode 'whizbang-mode 'lisp-mode 'perl-mode 'scheme-mode) - "List of modes to always start in font-lock-mode") - -This means that Emacs will always enable -font-lock-mode (ie syntax highlighting) when -editing a .wiz file. + "List of modes to always start in font-lock-mode") + -And that's all that's needed. If there's anything else you want -done automatically when you open up a .wiz file, -you can add a whizbang-mode hook (see -my-scheme-mode-hook for a simple example that -adds auto-indent). - - - + This means that Emacs will always enable + font-lock-mode (ie syntax highlighting) + when editing a .wiz file. - -Further Reading + And that's all that's needed. If there's anything else + you want done automatically when you open up a + .wiz file, you can add a + whizbang-mode hook (see + my-scheme-mode-hook for a simple example + that adds auto-indent). + + - -Brian Harvey and Matthew Wright -Simply Scheme -MIT 1994. -ISBN 0-262-08226-8 + + Further Reading -Randall Schwartz -Learning Perl -O'Reilly 1993 -ISBN 1-56592-042-2 + + + Brian Harvey and Matthew Wright + Simply Scheme + MIT 1994. + ISBN 0-262-08226-8 + -Patrick Henry Winston and Berthold Klaus Paul Horn -Lisp (3rd Edition) -Addison-Wesley 1989 -ISBN 0-201-08319-1 + + Randall Schwartz + Learning Perl + O'Reilly 1993 + ISBN 1-56592-042-2 + -Brian W. Kernighan and Rob Pike -The Unix Programming Environment -Prentice-Hall 1984 -ISBN 0-13-937681-X + + Patrick Henry Winston and Berthold Klaus Paul Horn + Lisp (3rd Edition) + Addison-Wesley 1989 + ISBN 0-201-08319-1 + -Brian W. Kernighan and Dennis M. Ritchie -The C Programming Language (2nd Edition) -Prentice-Hall 1988 -ISBN 0-13-110362-8 + + Brian W. Kernighan and Rob Pike + The Unix Programming Environment + Prentice-Hall 1984 + ISBN 0-13-937681-X + -Bjarne Stroustrup -The C++ Programming Language -Addison-Wesley 1991 -ISBN 0-201-53992-6 + + Brian W. Kernighan and Dennis M. Ritchie + The C Programming Language (2nd Edition) + Prentice-Hall 1988 + ISBN 0-13-110362-8 + -W. Richard Stevens -Advanced Programming in the Unix Environment -Addison-Wesley 1992 -ISBN 0-201-56317-7 + + Bjarne Stroustrup + The C++ Programming Language + Addison-Wesley 1991 + ISBN 0-201-53992-6 + -W. Richard Stevens -Unix Network Programming -Prentice-Hall 1990 -ISBN 0-13-949876-1 + + W. Richard Stevens + Advanced Programming in the Unix Environment + Addison-Wesley 1992 + ISBN 0-201-56317-7 + - - - + + W. Richard Stevens + Unix Network Programming + Prentice-Hall 1990 + ISBN 0-13-949876-1 + + +