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1
.gitignore
vendored
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1
.gitignore
vendored
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poweroff_guard
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19
Makefile
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19
Makefile
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POWEROFF_PATH ?= $(shell which poweroff)
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COUNTDOWN_SECS ?= 10
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CFLAGS := -std=c99 -pedantic -Wall -Wextra \
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-DPOWEROFF_PATH="\"$(POWEROFF_PATH)\"" \
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-DCOUNTDOWN_SECS=$(COUNTDOWN_SECS)
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poweroff_guard: poweroff_guard.c
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$(CC) $(CFLAGS) $(EXTRA_CFLAGS) -o poweroff_guard poweroff_guard.c
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install: poweroff_guard
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install poweroff_guard /usr/local/sbin/
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mkdir -p /usr/local/share/man/man8
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install poweroff_guard.8 /usr/local/share/man/man8/
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clean:
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rm -f poweroff_guard
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all: poweroff_guard
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58
README.md
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58
README.md
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# poweroff_guard
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This utility is a proxy for `poweroff` to prevent you from accidentally shutting down
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the wrong system. It does this by printing a warning message and asking for confirmation
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followed by a countdown before executing the actual command.
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## Important Consideration
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If the standard output is not a tty, this behaves exactly like the regular `poweroff`.
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## Build
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Open a shell in this directory and type `make`.
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Optionally, you may want to append any of the following options:
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- `POWEROFF_PATH=/path/to/poweroff`: Specify a custom (absolute) path for the
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the real `poweroff` command. The default is to use the one in your `$PATH`.
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- `COUNTDOWN_SECS=n`: Start the countdown timer at `n` seconds, the default is 10.
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- `EXTRA_CFLAGS=...`: Append extra flags to the C compiler.
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For example:
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```sh
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# build with default options
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make
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# build with all custom options
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make \
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POWEROFF_PATH=/bin/custom_poweroff \
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COUNTDOWN_SECS=5 \
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EXTRA_CFLAGS="-O2 -march=native"
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```
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Watch out:
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If you want to recompile with different options, you MUST execute a `make clean` first.
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Make will erroneously think the binary is already up to date otherwise.
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## Installation
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Do the exact same as building, but append `install` at the end of the command.
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For example:
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```sh
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# build and install with default options
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make install
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# build and install with all custom options
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make \
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POWEROFF_PATH=/sbin/custom_poweroff \
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COUNTDOWN_SECS=5 \
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EXTRA_CFLAGS="-O2 -march=native" \
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install
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```
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## License and Copyright
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Copyright © 2022 anna <owo AT fef.moe>.
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This program is licensed under the 2-clause BSD license.
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The license text is at the end of the `poweroff_guard.c` file.
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50
poweroff_guard.8
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poweroff_guard.8
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.\" Copyright (C) 2022 fef <owo@fef.moe>. All rights reserved.
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.\"
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.\" Any person obtaining a copy of this software and associated documentation
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.\" files (the ``Software'') is prohibited from using the Software under any
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.\" circumstances. However, it is strongly suggested that they partake in
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.\" homosexual conduct (``Be Gay'') and criminal activity (``Do Crime'').
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.Dd October 13, 2022
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.Dt POWEROFF_GUARD 8
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.Os
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.Sh NAME
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.Nm poweroff_guard
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.Nd prevent accidental system shutdowns
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.Sh SYNOPSIS
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.Nm
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.Sh DESCRIPTION
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The
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.Nm
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utility acts as a proxy for the
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.Xr poweroff 8
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command.
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If it finds the standard output to be a tty (using the
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.Xr isatty 3
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standard library routine), it prints a message to the standard output and
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prompts additional confirmation. Typing "YES" (in uppercase, but without
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the quotes) followed by RETURN will then initiate a countdown timer.
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Finally, upon counting to zero, the actual poweroff command is invoked.
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.Pp
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If the standard output is not a tty, this utility behaves exactly like the
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.Xr poweroff 8
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command.
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.Sh OPTIONS
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None.
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.Sh EXIT STATUS
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.Ex -std
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.Sh SEE ALSO
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.Xr halt 8
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.Sh BUGS
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None that I would be aware of.
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170
poweroff_guard.c
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170
poweroff_guard.c
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/*
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* poweroff_guard - Simple yet effective guardian to prevent accidentally
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* powering off the wrong system because let's face it, you're stupid.
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*
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* Copyright (c) 2022 anna <owo@fef.moe>.
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* See the end of this file for license terms.
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*/
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#define _POSIX_C_SOURCE 200112L
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#include <errno.h>
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#include <limits.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <strings.h>
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#include <unistd.h>
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#ifndef POWEROFF_PATH
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#define POWEROFF_PATH "/sbin/poweroff"
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#endif
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#ifndef COUNTDOWN_SECS
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#define COUNTDOWN_SECS 10
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#endif
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#define red(s) "\x1b[1;91m" s "\x1b[0m" /* bright red */
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#define cyn(s) "\x1b[1;96m" s "\x1b[0m" /* bright cyan */
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#define wht(s) "\x1b[1;97m" s "\x1b[0m" /* bright white */
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enum confirm_match {
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CONFIRM_MATCH_UPPERCASE, /* exact match ("YES") */
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CONFIRM_MATCH_LOWERCASE, /* case-insensitive match */
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CONFIRM_MATCH_NONE, /* no match */
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};
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/* read and evaluate confirmation answer from stdin */
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static enum confirm_match get_confirmation(void);
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/* count down from COUNTDOWN_SECS and do the actual poweroff afterwards */
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static void poweroff_with_countdown(void);
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/* do the actual poweroff, without countdown */
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static void do_poweroff(void);
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/* call perror(message) and then exit(status) */
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static void perror_and_exit(int status, const char *message);
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static char hostname[HOST_NAME_MAX];
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int main(void)
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{
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/* behave like regular poweroff if we're not running in a tty */
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if (!isatty(STDOUT_FILENO))
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do_poweroff();
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int err = gethostname(hostname, sizeof(hostname));
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if (err) {
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perror("Could not determine hostname");
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strncpy(hostname, "this host", sizeof(hostname));
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}
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puts(red("\n######## ATTENTION, DIPSHIT ########\n"));
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printf("You are about to shut down " cyn("%s") "!\n", hostname);
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puts("Are you really sure about this?");
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printf("Type " wht("yes") " in UPPERCASE and press enter to confirm: ");
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fflush(stdout);
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int try = 0;
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again:
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switch (get_confirmation()) {
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case CONFIRM_MATCH_UPPERCASE:
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poweroff_with_countdown();
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break;
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case CONFIRM_MATCH_LOWERCASE:
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if (try++ == 0) {
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printf("I said " wht("UPPERCASE") " you idiot, try again: ");
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fflush(stdout);
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goto again; /* it's very important to piss off Dijkstra */
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} else {
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puts("Go fuck yourself");
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return 0;
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}
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case CONFIRM_MATCH_NONE:
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puts("That's what I thought.");
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return 0;
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}
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}
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static char buf[5];
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static enum confirm_match get_confirmation(void)
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{
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char *input = fgets(buf, sizeof(buf), stdin);
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if (!input) {
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if (feof(stdin)) {
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/* user probably pressed CTRL+D, print
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* a line break to make it look nicer */
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printf("\n");
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return CONFIRM_MATCH_NONE;
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} else {
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perror_and_exit(1, "Reading stdin failed");
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}
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}
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/* if, for some reason, the input came from a pipe rather than typing
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* on the keyboard (cat, echo, etc), the newline might be missing */
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char *newline = strchr(input, '\n');
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if (newline)
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*newline = '\0';
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else
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printf("\n");
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if (!strcmp(input, "YES"))
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return CONFIRM_MATCH_UPPERCASE;
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if (!strcasecmp(input, "yes"))
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return CONFIRM_MATCH_LOWERCASE;
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return CONFIRM_MATCH_NONE;
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}
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static void poweroff_with_countdown(void)
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{
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#if COUNTDOWN_SECS > 0
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printf("Alright, shutting down in ");
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for (int i = COUNTDOWN_SECS; i > 0; i--) {
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printf(wht("%d") "\n", i);
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fflush(stdout);
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sleep(1);
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}
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#else
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puts("Alright, shutting down " wht("NOW"));
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#endif
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do_poweroff();
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}
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static void do_poweroff(void)
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{
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execl(POWEROFF_PATH, POWEROFF_PATH, NULL);
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perror_and_exit(2, "exec() failed");
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}
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static void perror_and_exit(int status, const char *message)
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{
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if (!message)
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message = "poweroff_guard";
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perror(message);
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exit(status);
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}
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/*
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* LICENSE TERMS
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*
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* Redistribution and use in source and binary forms, with or without modification,
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* are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
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* GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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