lib/subpipe.c

   1 /* Subprocesses with pipes.
   2
   3    Copyright (C) 2002, 2004, 2005 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 # 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
  75 /* Initialize this module.  */
  76
  77 void
  78 init_subpipe (void)
  79 {
  80 #ifdef SIGCHLD
  81   /* System V fork+wait does not work if SIGCHLD is ignored.  */
  82   signal (SIGCHLD, SIG_DFL);
  83 #endif
  84 }
  85
  86
  87 /* Create a subprocess that is run as a filter.  ARGV is the
  88    NULL-terminated argument vector for the subprocess.  Store read and
  89    write file descriptors for communication with the subprocess into
  90    FD[0] and FD[1]: input meant for the process can be written into
  91    FD[0], and output from the process can be read from FD[1].  Return
  92    the subprocess id.
  93
  94    To avoid deadlock, the invoker must not let incoming data pile up
  95    in FD[1] while writing data to FD[0].  */
  96
  97 pid_t
  98 create_subpipe (char const * const *argv, int fd[2])
  99 {
 100   int pipe_fd[2];
 101   int child_fd[2];
 102   pid_t pid;
 103
 104   if (pipe (child_fd) != 0
 105       || (child_fd[0] = fd_safer (child_fd[0])) < 0
 106       || (fd[0] = fd_safer (child_fd[1])) < 0
 107       || pipe (pipe_fd) != 0
 108       || (fd[1] = fd_safer (pipe_fd[0])) < 0
 109       || (child_fd[1] = fd_safer (pipe_fd[1])) < 0)
 110     error (EXIT_FAILURE, errno,
 111            "pipe");
 112
 113   pid = vfork ();
 114   if (pid < 0)
 115     error (EXIT_FAILURE, errno,
 116            "fork");
 117
 118   if (! pid)
 119     {
 120       /* Child.  */
 121       close (fd[0]);
 122       close (fd[1]);
 123       dup2 (child_fd[0], STDIN_FILENO);
 124       close (child_fd[0]);
 125       dup2 (child_fd[1], STDOUT_FILENO);
 126       close (child_fd[1]);
 127
 128       /* The cast to (char **) rather than (char * const *) is needed
 129          for portability to older hosts with a nonstandard prototype
 130          for execvp.  */
 131       execvp (argv[0], (char **) argv);
 132
 133       _exit (errno == ENOENT ? 127 : 126);
 134     }
 135
 136   /* Parent.  */
 137   close (child_fd[0]);
 138   close (child_fd[1]);
 139   return pid;
 140 }
 141
 142
 143 /* Wait for the subprocess to exit.  */
 144
 145 void
 146 reap_subpipe (pid_t pid, char const *program)
 147 {
 148 #if HAVE_WAITPID || defined waitpid
 149   int wstatus;
 150   if (waitpid (pid, &wstatus, 0) < 0)
 151     error (EXIT_FAILURE, errno,
 152            "waitpid");
 153   else
 154     {
 155       int status = WIFEXITED (wstatus) ? WEXITSTATUS (wstatus) : -1;
 156       if (status)
 157         error (EXIT_FAILURE, 0,
 158                _(status == 126
 159                  ? "subsidiary program `%s' could not be invoked"
 160                  : status == 127
 161                  ? "subsidiary program `%s' not found"
 162                  : status < 0
 163                  ? "subsidiary program `%s' failed"
 164                  : "subsidiary program `%s' failed (exit status %d)"),
 165                program, status);
 166     }
 167 #endif
 168 }