lib/subpipe.c

   1 /* Subprocesses with pipes.
   2
   3    Copyright (C) 2002, 2004 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 #if 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 # if HAVE_FCNTL_H
  48 #  include <fcntl.h>
  49 # endif
  50 # define dup2(f, t) (close (t), fcntl (f, F_DUPFD, t))
  51 #endif
  52
  53 #if HAVE_SYS_WAIT_H
  54 # include <sys/wait.h>
  55 #endif
  56 #ifndef WEXITSTATUS
  57 # define WEXITSTATUS(stat_val) ((unsigned int) (stat_val) >> 8)
  58 #endif
  59 #ifndef WIFEXITED
  60 # define WIFEXITED(stat_val) (((stat_val) & 255) == 0)
  61 #endif
  62
  63 #if HAVE_VFORK_H
  64 # include <vfork.h>
  65 #endif
  66 #if ! HAVE_WORKING_VFORK
  67 # define vfork fork
  68 #endif
  69
  70 #include "error.h"
  71
  72 #include "gettext.h"
  73 #define _(Msgid)  gettext (Msgid)
  74
  75
  76 /* Initialize this module.  */
  77
  78 void
  79 init_subpipe (void)
  80 {
  81 #ifdef SIGCHLD
  82   /* System V fork+wait does not work if SIGCHLD is ignored.  */
  83   signal (SIGCHLD, SIG_DFL);
  84 #endif
  85 }
  86
  87
  88 /* Create a subprocess that is run as a filter.  ARGV is the
  89    NULL-terminated argument vector for the subprocess.  Store read and
  90    write file descriptors for communication with the subprocess into
  91    FD[0] and FD[1]: input meant for the process can be written into
  92    FD[0], and output from the process can be read from FD[1].  Return
  93    the subprocess id.
  94
  95    To avoid deadlock, the invoker must not let incoming data pile up
  96    in FD[1] while writing data to FD[0].  */
  97
  98 pid_t
  99 create_subpipe (char const * const *argv, int fd[2])
 100 {
 101   int pipe_fd[2];
 102   int from_in_fd;
 103   int from_out_fd;
 104   int to_in_fd;
 105   int to_out_fd;
 106   pid_t pid;
 107
 108   if (pipe (pipe_fd) != 0)
 109     error (EXIT_FAILURE, errno, "pipe");
 110   to_in_fd = pipe_fd[0];
 111   to_out_fd = pipe_fd[1];
 112
 113   if (pipe (pipe_fd) != 0)
 114     error (EXIT_FAILURE, errno, "pipe");
 115   from_in_fd = pipe_fd[0];
 116   from_out_fd = pipe_fd[1];
 117
 118   pid = vfork ();
 119   if (pid < 0)
 120     error (EXIT_FAILURE, errno, "fork");
 121
 122   if (! pid)
 123     {
 124       /* Child.  */
 125       close (to_out_fd);
 126       close (from_in_fd);
 127
 128       if (to_in_fd != STDIN_FILENO)
 129         {
 130           dup2 (to_in_fd, STDIN_FILENO);
 131           close (to_in_fd);
 132         }
 133       if (from_out_fd != STDOUT_FILENO)
 134         {
 135           dup2 (from_out_fd, STDOUT_FILENO);
 136           close (from_out_fd);
 137         }
 138
 139       /* The cast to (char **) rather than (char * const *) is needed
 140          for portability to older hosts with a nonstandard prototype
 141          for execvp.  */
 142       execvp (argv[0], (char **) argv);
 143
 144       _exit (errno == ENOENT ? 127 : 126);
 145     }
 146
 147   /* Parent.  */
 148   close (to_in_fd);
 149   close (from_out_fd);
 150   fd[0] = to_out_fd;
 151   fd[1] = from_in_fd;
 152   return pid;
 153 }
 154
 155
 156 /* Wait for the subprocess to exit.  */
 157
 158 void
 159 reap_subpipe (pid_t pid, char const *program)
 160 {
 161 #if HAVE_WAITPID || defined waitpid
 162   int wstatus;
 163   if (waitpid (pid, &wstatus, 0) < 0)
 164     error (EXIT_FAILURE, errno, "waitpid");
 165   else
 166     {
 167       int status = WIFEXITED (wstatus) ? WEXITSTATUS (wstatus) : -1;
 168       if (status)
 169         error (EXIT_FAILURE, 0,
 170                _(status == 126
 171                  ? "subsidiary program `%s' could not be invoked"
 172                  : status == 127
 173                  ? "subsidiary program `%s' not found"
 174                  : status < 0
 175                  ? "subsidiary program `%s' failed"
 176                  : "subsidiary program `%s' failed (exit status %d)"),
 177                program, status);
 178     }
 179 #endif
 180 }