lib/subpipe.c

   1 /* Subprocesses with pipes.
   2
   3    Copyright (C) 2002, 2004, 2005, 2006 Free Software Foundation, Inc.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 2, or (at your option)
   8    any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, write to the Free Software Foundation,
  17    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  18
  19 /* Written by Paul Eggert <eggert@twinsun.com>
  20    and Florian Krohm <florian@edamail.fishkill.ibm.com>.  */
  21
  22 #ifdef HAVE_CONFIG_H
  23 # include <config.h>
  24 #endif
  25
  26 #include "subpipe.h"
  27
  28 #include <errno.h>
  29
  30 #include <signal.h>
  31 #if ! defined SIGCHLD && defined SIGCLD
  32 # define SIGCHLD SIGCLD
  33 #endif
  34
  35 #include <stdlib.h>
  36
  37 #if HAVE_UNISTD_H
  38 # include <unistd.h>
  39 #endif
  40 #ifndef STDIN_FILENO
  41 # define STDIN_FILENO 0
  42 #endif
  43 #ifndef STDOUT_FILENO
  44 # define STDOUT_FILENO 1
  45 #endif
  46 #if ! HAVE_DUP2 && ! defined dup2
  47 # include <fcntl.h>
  48 # define dup2(f, t) (close (t), fcntl (f, F_DUPFD, t))
  49 #endif
  50
  51 #if HAVE_SYS_WAIT_H
  52 # include <sys/wait.h>
  53 #endif
  54 #ifndef WEXITSTATUS
  55 # define WEXITSTATUS(stat_val) ((unsigned int) (stat_val) >> 8)
  56 #endif
  57 #ifndef WIFEXITED
  58 # define WIFEXITED(stat_val) (((stat_val) & 255) == 0)
  59 #endif
  60
  61 #if HAVE_VFORK_H
  62 # include <vfork.h>
  63 #endif
  64 #if ! HAVE_WORKING_VFORK
  65 # define vfork fork
  66 #endif
  67
  68 #include "error.h"
  69 #include "unistd-safer.h"
  70
  71 #include "gettext.h"
  72 #define _(Msgid)  gettext (Msgid)
  73
  74 #ifndef __attribute__
  75 /* This feature is available in gcc versions 2.5 and later.  */
  76 # if ! defined __GNUC__ || __GNUC__ < 2 || \
  77 (__GNUC__ == 2 && __GNUC_MINOR__ < 5) || __STRICT_ANSI__
  78 #  define __attribute__(Spec) /* empty */
  79 # endif
  80 #endif
  81
  82 #ifndef ATTRIBUTE_UNUSED
  83 # define ATTRIBUTE_UNUSED __attribute__ ((__unused__))
  84 #endif
  85
  86
  87 /* Initialize this module.  */
  88
  89 void
  90 init_subpipe (void)
  91 {
  92 #ifdef SIGCHLD
  93   /* System V fork+wait does not work if SIGCHLD is ignored.  */
  94   signal (SIGCHLD, SIG_DFL);
  95 #endif
  96 }
  97
  98
  99 /* Create a subprocess that is run as a filter.  ARGV is the
 100    NULL-terminated argument vector for the subprocess.  Store read and
 101    write file descriptors for communication with the subprocess into
 102    FD[0] and FD[1]: input meant for the process can be written into
 103    FD[0], and output from the process can be read from FD[1].  Return
 104    the subprocess id.
 105
 106    To avoid deadlock, the invoker must not let incoming data pile up
 107    in FD[1] while writing data to FD[0].  */
 108
 109 pid_t
 110 create_subpipe (char const * const *argv, int fd[2])
 111 {
 112   int pipe_fd[2];
 113   int child_fd[2];
 114   pid_t pid;
 115
 116   if (pipe_safer (child_fd) != 0 || pipe_safer (pipe_fd) != 0)
 117     error (EXIT_FAILURE, errno, "pipe");
 118   fd[0] = child_fd[1];
 119   fd[1] = pipe_fd[0];
 120   child_fd[1] = pipe_fd[1];
 121
 122   pid = vfork ();
 123   if (pid < 0)
 124     error (EXIT_FAILURE, errno, "fork");
 125
 126   if (! pid)
 127     {
 128       /* Child.  */
 129       close (fd[0]);
 130       close (fd[1]);
 131       dup2 (child_fd[0], STDIN_FILENO);
 132       close (child_fd[0]);
 133       dup2 (child_fd[1], STDOUT_FILENO);
 134       close (child_fd[1]);
 135
 136       /* The cast to (char **) rather than (char * const *) is needed
 137          for portability to older hosts with a nonstandard prototype
 138          for execvp.  */
 139       execvp (argv[0], (char **) argv);
 140
 141       _exit (errno == ENOENT ? 127 : 126);
 142     }
 143
 144   /* Parent.  */
 145   close (child_fd[0]);
 146   close (child_fd[1]);
 147   return pid;
 148 }
 149
 150
 151 /* Wait for the subprocess to exit.  */
 152
 153 void
 154 reap_subpipe (pid_t pid, char const *program)
 155 {
 156 #if HAVE_WAITPID || defined waitpid
 157   int wstatus;
 158   if (waitpid (pid, &wstatus, 0) < 0)
 159     error (EXIT_FAILURE, errno, "waitpid");
 160   else
 161     {
 162       int status = WIFEXITED (wstatus) ? WEXITSTATUS (wstatus) : -1;
 163       if (status)
 164         error (EXIT_FAILURE, 0,
 165                _(status == 126
 166                  ? "subsidiary program `%s' could not be invoked"
 167                  : status == 127
 168                  ? "subsidiary program `%s' not found"
 169                  : status < 0
 170                  ? "subsidiary program `%s' failed"
 171                  : "subsidiary program `%s' failed (exit status %d)"),
 172                program, status);
 173     }
 174 #endif
 175 }
 176
 177 void
 178 end_of_output_subpipe (pid_t pid ATTRIBUTE_UNUSED,
 179                        int fd[2] ATTRIBUTE_UNUSED)
 180 {
 181 }