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