From 7b6c6008e0e3f2a88c974cf8bea0545037626d2c Mon Sep 17 00:00:00 2001 From: joeyh Date: Fri, 8 Sep 2006 00:33:43 +0000 Subject: * Add mispipe, contributed by Nathanael Nerode. Pipes together two commands, returning the exit status of the first. --- mispipe.c | 179 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 179 insertions(+) create mode 100644 mispipe.c (limited to 'mispipe.c') diff --git a/mispipe.c b/mispipe.c new file mode 100644 index 0000000..43ba76a --- /dev/null +++ b/mispipe.c @@ -0,0 +1,179 @@ +/* + * 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 + * Run | , but return with the exit status of . + * + * 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 */ +#include +#include /* pipe(), fork(),... */ +#include /* system() */ +#include /* waitpid(), etc. */ +#include +#include /* 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 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. */ + system(cmd); + /* Close all the file descriptors. */ + if (close(filedes[0])) + error_with_errno("Failed (in child) closing filedes[0]" + " (while cleaning up)"); + 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 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 the pipe "standard output". */ + if (close(filedes[1])) + error_with_errno("Failed closing filedes[1] (while cleaning up)"); + /* 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); +} -- cgit v1.2.3