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/*
* mispipe: written by Nathanael Nerode.
*
* Copyright 2004 Nathanael Nerode.
*
* Licensed under the GPL version 2 or above, and dual-licensed under the
* following license:
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
/*
* Usage: mispipe <command1> <command2>
* Run <command1> | <command2>, but return with the exit status of <command1>.
*
* This is designed for a very specific purpose: logging.
* "foo | logger -t foo"
* will return with the exit status of logger, not that of foo.
* "mispipe foo 'logger -t foo'"
* will return with the exit status of foo.
*/
/*
* To do:
* Make this into a fancy, internationalized, option-handling hellbeast.
* (But why bother? It does its job quite well.)
*/
#include <errno.h> /* errno */
#include <sys/types.h>
#include <unistd.h> /* pipe(), fork(),... */
#include <stdlib.h> /* system() */
#include <sys/wait.h> /* waitpid(), etc. */
#include <stdio.h>
#include <stdarg.h> /* va_list, for error() */
static const char* progname; /* Stores argv[0] */
static int filedes[2]; /* Stores pipe file descriptors */
/* Subroutine for 'warning' and 'error' which prefixes progname */
static void warning_prefix(void) {
fputs(progname, stderr);
fputs(": ", stderr);
}
/* Issue a warning, then die */
__attribute__(( noreturn, format (printf, 1, 2) ))
static void error(const char* formatstr, ...) {
va_list ap;
va_start(ap, formatstr);
warning_prefix();
vfprintf(stderr, formatstr, ap);
va_end(ap);
exit(1);
}
/* Issue a warning, then die, with errno */
__attribute__(( noreturn ))
static void error_with_errno(const char* message) {
int saved_errno;
saved_errno=errno;
warning_prefix();
fputs(message, stderr);
fputs(": error number ", stderr);
fprintf(stderr, "%i\n", saved_errno);
exit(1);
}
/* Convert 'wait'/'system'-style exit status to 'exit'-style exit status */
__attribute__(( const ))
static int shorten_status(int status_big) {
if (WIFEXITED(status_big))
return WEXITSTATUS(status_big);
if (WIFSIGNALED(status_big))
return 128+WTERMSIG(status_big);
if (WIFSTOPPED(status_big))
return 128+WSTOPSIG(status_big);
#ifdef WCOREDUMP
if (WCOREDUMP(status_big))
error("Ow, somebody dumped core!");
#endif
error("shorten_status got an invalid status (?!)");
}
/* All the work for command 2. */
__attribute__(( noreturn ))
static void subprocess2(const char* cmd) {
/* Close the old standard input. */
if (close(0))
error_with_errno("Failed (in child) closing standard input");
/* Make the reading end of the pipe the new standard input. */
if (dup2(filedes[0], 0) == -1)
error_with_errno("Failed (in child) redefining standard input");
/* Close the original file descriptor for it */
if (close(filedes[0]))
error_with_errno("Failed (in child) closing filedes[0]");
/* Close the other end of the pipe. */
if (close(filedes[1]))
error_with_errno("Failed (in child) closing filedes[1]");
/* Do the second command, and throw away the exit status. */
if (system(cmd)) {}
/* Close the standard input. */
if (close(0))
error_with_errno("Failed (in child) closing standard output "
" (while cleaning up)");
exit(0);
}
int main (int argc, const char ** argv) {
int status_big; /* Exit status, 'wait' and 'system' style */
pid_t child2_pid;
pid_t dead_pid;
/* Set progname */
progname = argv[0];
/* Verify arguments */
if (argc != 3)
error("Wrong number of args, aborting\n");
/* Open a new pipe */
if (pipe(filedes))
error_with_errno("pipe() failed");
/* Fork to run second command */
child2_pid = fork();
if (child2_pid == 0)
subprocess2(argv[2]);
if (child2_pid == -1)
error_with_errno("fork() failed");
/* Run first command inline (seriously!) */
/* Close standard output. */
if (close(1))
error_with_errno("Failed closing standard output");
/* Make the writing end of the pipe the new standard output. */
if (dup2(filedes[1], 1) == -1)
error_with_errno("Failed redefining standard output");
/* Close the original file descriptor for it. */
if (close(filedes[1]))
error_with_errno("Failed closing filedes[1]");
/* Close the other end of the pipe. */
if (close(filedes[0]))
error_with_errno("Failed closing filedes[0]");
/* Do the first command, and (crucially) get the status. */
status_big = system(argv[1]);
/* Close standard output. */
if (close(1))
error_with_errno("Failed closing standard output (while cleaning up)");
/* Wait for the other process to exit. */
/* We don't care about the status. */
dead_pid = waitpid(child2_pid, NULL, WUNTRACED);
if (dead_pid == -1) {
error_with_errno("waitpid() failed");
}
else if (dead_pid != child2_pid) {
error("waitpid(): Who died? %i\n", dead_pid);
}
/* Return the desired exit status. */
return shorten_status(status_big);
}
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