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11136: Reorganize history expansion doc.
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Bart Schaefer
parent
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commit
09b09770d9
2 changed files with 111 additions and 84 deletions
191
Doc/Zsh/expn.yo
191
Doc/Zsh/expn.yo
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@ -49,36 +49,91 @@ cindex(expansion, history)
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History expansion allows you to use words from previous command
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lines in the command line you are typing. This simplifies spelling
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corrections and the repetition of complicated commands or arguments.
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Command lines are saved in the history list, the size of which
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is controlled by the tt(HISTSIZE)
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vindex(HISTSIZE, use of)
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parameter. The most recent command is retained in any case.
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A history expansion begins with the first character of the
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tt(histchars) parameter which is `tt(!)'
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by default and may occur anywhere on the command line; history
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expansions do not nest. The `tt(!)' can be escaped with `tt(\)'
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or can be enclosed between a pair of single quotes (tt('')) to suppress
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its special meaning. Double quotes will em(not) work for this.
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Immediately before execution, each command is saved in the history list,
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the size of which is controlled by the tt(HISTSIZE) parameter. The one
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most recent command is always retained in any case. Each saved command in
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the history list is called a history em(event) and is assigned a number,
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beginning with 1 (one) when the shell starts up. The history number that
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you may see in your prompt (see noderef(Prompt Expansion)) is the number
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that is to be assigned to the em(next) command.
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Input lines containing history expansions are echoed on the
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terminal after being expanded, but before any other
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expansions take place or the command gets executed.
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startmenu()
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menu(Overview)
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menu(Event Designators)
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menu(Word Designators)
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menu(Modifiers)
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endmenu()
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texinode(Event Designators)(Word Designators)()(History Expansion)
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texinode(Overview)(Event Designators)()(History Expansion)
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subsect(Overview)
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vindex(histchars, use of)
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A history expansion begins with the first character of the tt(histchars)
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parameter, which is `tt(!)' by default, and may occur anywhere on the
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command line; history expansions do not nest. The `tt(!)' can be escaped
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with `tt(\)' or can be enclosed between a pair of single quotes (tt(''))
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to suppress its special meaning. Double quotes will em(not) work for
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this. Following this history character is an optional event designator
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(ifzman(see )noderef(Event Designators)) and then an optional word
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designator (noderef(Word Designators)); if neither of these designators is
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present, no history expansion occurs.
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Input lines containing history expansions are echoed after being expanded,
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but before any other expansions take place and before the command is
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executed. It is this expanded form that is recorded as the history event
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for later references.
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By default, a history reference with no event designator refers to the
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same event as any preceding history reference on that command line; if it
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is the only history reference in a command, it refers to the previous
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command.
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pindex(CSH_JUNKIE_HISTORY, use of)
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However, if the option tt(CSH_JUNKIE_HISTORY) is set, then every history
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reference with no event specification em(always) refers to the previous
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command.
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For example, `tt(!)' is the event designator for the previous command, so
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`tt(!!:1)' always refers to the first word of the previous command, and
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`tt(!!$)' always refers to the last word of the previous command. With
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tt(CSH_JUNKIE_HISTORY) set, then `tt(!:1)' and `tt(!$)' function in the
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same manner as `tt(!!:1)' and `tt(!!$)', respectively. Conversely, if
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tt(CSH_JUNKIE_HISTORY) is unset, then `tt(!:1)' and `tt(!$)' refer to the
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first and last words, respectively, of the same event referenced by the
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nearest other history reference preceding them on the current command
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line, or to the previous command if there is no preceding reference.
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The character sequence `tt(^)var(foo)tt(^)var(bar)' (where `tt(^)' is
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actually the second charcter of the tt(histchars) parameter)
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repeats the last command, replacing the string var(foo) with var(bar).
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More precisely, the sequence `tt(^)var(foo)tt(^)var(bar)tt(^)' is
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synonymous with `tt(!!:s)tt(^)var(foo)tt(^)var(bar)tt(^)', hence other
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modifiers (see noderef(Modifiers)) may follow the final `tt(^)'.
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If the shell encounters the character sequence `tt(!")'
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in the input, the history mechanism is temporarily disabled until
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the current list (see
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ifzman(manref(zshmisc))\
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ifnzman(noderef(Shell Grammar))\
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) is fully parsed. The `tt(!")' is removed from the input, and any
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subsequent `tt(!)' characters have no special significance.
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findex(fc, use of)
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A less convenient but more comprehensible form of command history support
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is provided by the tt(fc) builtin.
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texinode(Event Designators)(Word Designators)(Overview)(History Expansion)
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subsect(Event Designators)
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cindex(history event designators)
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cindex(event designators, history)
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An event designator is a reference to a command-line entry in
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the history list.
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An event designator is a reference to a command-line entry in the history
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list. In the list below, remember that the initial tt(`!') in each item
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may be changed to another character by setting the tt(histchars)
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parameter.
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startitem()
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item(tt(!))(
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Start a history expansion, except when followed by a blank, newline,
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`tt(=)' or `tt(LPAR())'.
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`tt(=)' or `tt(LPAR())'. If followed immediately by a word designator
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(ifzman(see )noderef(Word Designators)), this forms a history reference
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with no event designator (ifzman(see )noderef(Overview)).
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)
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item(tt(!!))(
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Refer to the previous command.
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@ -95,7 +150,9 @@ item(tt(!)var(str))(
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Refer to the most recent command starting with var(str).
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)
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item(tt(!?)var(str)[tt(?)])(
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Refer to the most recent command containing var(str).
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Refer to the most recent command containing var(str). The trailing
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`tt(?)' is necessary if this reference is to be followed by a modifier or
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followed by any text that is not to be considered part of var(str).
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)
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item(tt(!#))(
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Refer to the current command line typed in so far. The line is
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@ -110,10 +167,10 @@ texinode(Word Designators)(Modifiers)(Event Designators)(History Expansion)
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subsect(Word Designators)
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cindex(history word designators)
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cindex(word designators, history)
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A word designator indicates which word or words of a given command line will
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be included in a history reference. A `tt(:)'
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A word designator indicates which word or words of a given command line are
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to be included in a history reference. A `tt(:)' usually
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separates the event specification from the word designator.
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It can be omitted if the word designator begins with a
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It may be omitted only if the word designator begins with a
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`tt(^)', `tt($)', `tt(*)', `tt(-)' or `tt(%)'.
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Word designators include:
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@ -129,9 +186,9 @@ sitem(var(x)tt(*))(Abbreviates `var(x)tt(-$)'.)
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sitem(var(x)tt(-))(Like `var(x)tt(*)' but omitting word tt($).)
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endsitem()
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Note that a `tt(%)' word designator will only work when used as
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`tt(!%)', `tt(!:%)' or `tt(!?)var(str)tt(?:%)',
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and only when used after a tt(!?) expansion. Anything else will result
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Note that a `tt(%)' word designator works only when used in one of
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`tt(!%)', `tt(!:%)' or `tt(!?)var(str)tt(?:%)', and only when used after a
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tt(!?) expansion (possibly in an earlier command). Anything else results
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in an error, although the error may not be the most obvious one.
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texinode(Modifiers)()(Word Designators)(History Expansion)
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subsect(Modifiers)
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@ -179,30 +236,6 @@ Convert the words to all lowercase.
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item(tt(u))(
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Convert the words to all uppercase.
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)
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item(tt(f))(
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(This and the following
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tt(F), tt(w) and tt(W) modifier only work with parameter expansion and
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filename generation.)
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Repeats the immediately (without a colon) following modifier until the
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resulting word doesn't change any more.
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)
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item(tt(F:)var(expr)tt(:))(
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Like tt(f), but repeats only var(n) times if the expression
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var(expr) evaluates to var(n). Any character can be used instead of
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the `tt(:)'; if `tt(LPAR())', `tt([)', or `tt({)'
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is used as the opening delimiter,
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the closing delimiter should be 'tt(RPAR())', `tt(])', or `tt(})',
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respectively.
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)
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item(tt(w))(
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Makes the immediately following modifier work on each word in the
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string.
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)
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item(tt(W:)var(sep)tt(:))(
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Like tt(w) but words are considered to be the parts of the string
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that are separated by var(sep). Any character can be used instead of
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the `tt(:)'; opening parentheses are handled specially, see above.
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)
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item(tt(s/)var(l)tt(/)var(r)[tt(/)])(
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Substitute var(r) for var(l) as described below.
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Unless preceded immediately by a tt(g), with no colon between,
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@ -231,43 +264,33 @@ the rightmost `tt(?)' in a context scan can similarly be omitted.
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Note the same record of the last var(l) and var(r) is maintained
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across all forms of expansion.
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By default, a history reference with no event specification refers to the same
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line as the previous history reference on that command line, unless it is the
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first history reference in a command. In that case, a history reference
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with no event specification always refers to the previous command. However,
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if the option tt(CSH_JUNKIE_HISTORY) is set,
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pindex(CSH_JUNKIE_HISTORY, use of)
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then history reference with no
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event specification will em(always) refer to the previous command.
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The following tt(f), tt(F), tt(w) and tt(W) modifiers work only with
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parameter expansion and filename generation. They are listed here to
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provide a single point of reference for all modifiers.
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For example, `tt(!!:1)'
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will always refer to the first word of the previous command, and `tt(!!$)'
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will always refer to the last word of the previous command. And with
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tt(CSH_JUNKIE_HISTORY) set, then `tt(!:1)' and `tt(!$)'
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will function in the same manner as `tt(!!:1)' and `tt(!!$)',
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respectively. However, if tt(CSH_JUNKIE_HISTORY) is unset, then
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`tt(!:1)' and `tt(!$)'
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will refer to the first and last words respectively, of the last command
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referenced on the current command line. However, if they are the first history
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reference on the command line, then they refer to the previous command.
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The character sequence `tt(^)var(foo)tt(^)var(bar)' (where `tt(^)' is
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actually the second charcter of the tt(histchars) parameter)
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repeats the last command, replacing the string var(foo) with var(bar).
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More precisely, the sequence `tt(^)var(foo)tt(^)var(bar)tt(^)' is
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synonymous with `tt(!!:s)tt(^)var(foo)tt(^)var(bar)tt(^)', hence other
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modifiers may follow the final `tt(^)'.
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If the shell encounters the character sequence `tt(!")'
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in the input, the history mechanism is temporarily disabled until
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the current list is fully parsed. The `tt(!")'
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is removed from the input, and any subsequent `tt(!)'
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characters have no special significance.
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A less convenient but more comprehensible
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form of command history support
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is provided by the tt(fc) builtin.
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findex(fc, use of)
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startitem()
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item(tt(f))(
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Repeats the immediately (without a colon) following modifier until the
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resulting word doesn't change any more.
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)
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item(tt(F:)var(expr)tt(:))(
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Like tt(f), but repeats only var(n) times if the expression
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var(expr) evaluates to var(n). Any character can be used instead of
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the `tt(:)'; if `tt(LPAR())', `tt([)', or `tt({)'
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is used as the opening delimiter,
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the closing delimiter should be 'tt(RPAR())', `tt(])', or `tt(})',
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respectively.
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)
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item(tt(w))(
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Makes the immediately following modifier work on each word in the
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string.
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)
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item(tt(W:)var(sep)tt(:))(
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Like tt(w) but words are considered to be the parts of the string
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that are separated by var(sep). Any character can be used instead of
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the `tt(:)'; opening parentheses are handled specially, see above.
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)
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enditem()
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texinode(Process Substitution)(Parameter Expansion)(History Expansion)(Expansion)
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sect(Process Substitution)
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cindex(process substitution)
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@ -277,7 +300,7 @@ Each command argument of the form
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`tt(>LPAR())var(list)tt(RPAR())' or
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`tt(=LPAR())var(list)tt(RPAR())'
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is subject to process substitution.
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In the case of the tt(<) or tt(>) forms, the shell will run process
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In the case of the tt(<) or tt(>) forms, the shell runs process
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var(list) asynchronously. If the system supports the tt(/dev/fd)
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mechanism, the command argument is the name of the device file
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corresponding to a file descriptor; otherwise, if the system supports named
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