lib/subpipe.c

   1 /* Subprocesses with pipes.
   2
   3    Copyright (C) 2002 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, 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 #if HAVE_SYS_TYPES_H
  27 # include <sys/types.h>
  28 #endif
  29
  30 #include <errno.h>
  31 #ifndef errno
  32 extern int errno;
  33 #endif
  34
  35 #include <signal.h>
  36 #if ! defined SIGCHLD && defined SIGCLD
  37 # define SIGCHLD SIGCLD
  38 #endif
  39
  40 #if HAVE_STDLIB_H
  41 # include <stdlib.h>
  42 #endif
  43 /* The following test is to work around the gross typo in
  44    systems like Sony NEWS-OS Release 4.0C, whereby EXIT_FAILURE
  45    is defined to 0, not 1.  */
  46 #if ! EXIT_FAILURE
  47 # undef EXIT_FAILURE
  48 # define EXIT_FAILURE 1
  49 #endif
  50
  51 #if HAVE_UNISTD_H
  52 # include <unistd.h>
  53 #endif
  54 #ifndef STDIN_FILENO
  55 # define STDIN_FILENO 0
  56 #endif
  57 #ifndef STDOUT_FILENO
  58 # define STDOUT_FILENO 1
  59 #endif
  60 #if ! HAVE_DUP2 && ! defined dup2
  61 # if HAVE_FCNTL_H
  62 #  include <fcntl.h>
  63 # endif
  64 # define dup2(f, t) (close (t), fcntl (f, F_DUPFD, t))
  65 #endif
  66
  67 #if HAVE_SYS_WAIT_H
  68 # include <sys/wait.h>
  69 #endif
  70 #ifndef WEXITSTATUS
  71 # define WEXITSTATUS(stat_val) ((unsigned int) (stat_val) >> 8)
  72 #endif
  73 #ifndef WIFEXITED
  74 # define WIFEXITED(stat_val) (((stat_val) & 255) == 0)
  75 #endif
  76
  77 #if HAVE_VFORK_H
  78 # include <vfork.h>
  79 #endif
  80 #if ! HAVE_WORKING_VFORK
  81 # define vfork fork
  82 #endif
  83
  84 #include "error.h"
  85
  86 #include "gettext.h"
  87 #define _(Msgid)  gettext (Msgid)
  88
  89 #include "subpipe.h"
  90
  91
  92 /* Initialize this module.  */
  93
  94 void
  95 init_subpipe (void)
  96 {
  97 #ifdef SIGCHLD
  98   /* System V fork+wait does not work if SIGCHLD is ignored.  */
  99   signal (SIGCHLD, SIG_DFL);
 100 #endif
 101 }
 102
 103
 104 /* Create a subprocess that is run as a filter.  ARGV is the
 105    NULL-terminated argument vector for the subprocess.  Store read and
 106    write file descriptors for communication with the subprocess into
 107    FD[0] and FD[1]: input meant for the process can be written into
 108    FD[0], and output from the process can be read from FD[1].  Return
 109    the subprocess id.
 110
 111    To avoid deadlock, the invoker must not let incoming data pile up
 112    in FD[1] while writing data to FD[0].  */
 113
 114 pid_t
 115 create_subpipe (char const * const *argv, int fd[2])
 116 {
 117   int pipe_fd[2];
 118   int from_in_fd;
 119   int from_out_fd;
 120   int to_in_fd;
 121   int to_out_fd;
 122   pid_t pid;
 123
 124   if (pipe (pipe_fd) != 0)
 125     error (EXIT_FAILURE, errno, "pipe");
 126   to_in_fd = pipe_fd[0];
 127   to_out_fd = pipe_fd[1];
 128
 129   if (pipe (pipe_fd) != 0)
 130     error (EXIT_FAILURE, errno, "pipe");
 131   from_in_fd = pipe_fd[0];
 132   from_out_fd = pipe_fd[1];
 133
 134   pid = vfork ();
 135   if (pid < 0)
 136     error (EXIT_FAILURE, errno, "fork");
 137
 138   if (! pid)
 139     {
 140       /* Child.  */
 141       close (to_out_fd);
 142       close (from_in_fd);
 143
 144       if (to_in_fd != STDIN_FILENO)
 145         {
 146           dup2 (to_in_fd, STDIN_FILENO);
 147           close (to_in_fd);
 148         }
 149       if (from_out_fd != STDOUT_FILENO)
 150         {
 151           dup2 (from_out_fd, STDOUT_FILENO);
 152           close (from_out_fd);
 153         }
 154
 155       /* The cast to (char **) rather than (char * const *) is needed
 156          for portability to older hosts with a nonstandard prototype
 157          for execvp.  */
 158       execvp (argv[0], (char **) argv);
 159
 160       _exit (errno == ENOENT ? 127 : 126);
 161     }
 162
 163   /* Parent.  */
 164   close (to_in_fd);
 165   close (from_out_fd);
 166   fd[0] = to_out_fd;
 167   fd[1] = from_in_fd;
 168   return pid;
 169 }
 170
 171
 172 /* Wait for the subprocess to exit.  */
 173
 174 void
 175 reap_subpipe (pid_t pid, char const *program)
 176 {
 177 #if HAVE_WAITPID || defined waitpid
 178   int wstatus;
 179   if (waitpid (pid, &wstatus, 0) < 0)
 180     error (EXIT_FAILURE, errno, "waitpid");
 181   else
 182     {
 183       int status = WIFEXITED (wstatus) ? WEXITSTATUS (wstatus) : -1;
 184       if (status)
 185         error (EXIT_FAILURE, 0,
 186                _(status == 126
 187                  ? "subsidiary program `%s' could not be invoked"
 188                  : status == 127
 189                  ? "subsidiary program `%s' not found"
 190                  : status < 0
 191                  ? "subsidiary program `%s' failed"
 192                  : "subsidiary program `%s' failed (exit status %d)"),
 193                program, status);
 194     }
 195 #endif
 196 }