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 #include <unistd.h>
  38 #ifndef STDIN_FILENO
  39 # define STDIN_FILENO 0
  40 #endif
  41 #ifndef STDOUT_FILENO
  42 # define STDOUT_FILENO 1
  43 #endif
  44 #if ! HAVE_DUP2 && ! defined dup2
  45 # include <fcntl.h>
  46 # define dup2(f, t) (close (t), fcntl (f, F_DUPFD, t))
  47 #endif
  48
  49 #if HAVE_SYS_WAIT_H
  50 # include <sys/wait.h>
  51 #endif
  52 #ifndef WEXITSTATUS
  53 # define WEXITSTATUS(stat_val) ((unsigned int) (stat_val) >> 8)
  54 #endif
  55 #ifndef WIFEXITED
  56 # define WIFEXITED(stat_val) (((stat_val) & 255) == 0)
  57 #endif
  58
  59 #if HAVE_VFORK_H
  60 # include <vfork.h>
  61 #endif
  62 #if ! HAVE_WORKING_VFORK
  63 # define vfork fork
  64 #endif
  65
  66 #include "error.h"
  67 #include "unistd-safer.h"
  68
  69 #include "gettext.h"
  70 #define _(Msgid)  gettext (Msgid)
  71
  72 #ifndef __attribute__
  73 /* This feature is available in gcc versions 2.5 and later.  */
  74 # if ! defined __GNUC__ || __GNUC__ < 2 || \
  75 (__GNUC__ == 2 && __GNUC_MINOR__ < 5) || __STRICT_ANSI__
  76 #  define __attribute__(Spec) /* empty */
  77 # endif
  78 #endif
  79
  80 #ifndef ATTRIBUTE_UNUSED
  81 # define ATTRIBUTE_UNUSED __attribute__ ((__unused__))
  82 #endif
  83
  84
  85 /* Initialize this module.  */
  86
  87 void
  88 init_subpipe (void)
  89 {
  90 #ifdef SIGCHLD
  91   /* System V fork+wait does not work if SIGCHLD is ignored.  */
  92   signal (SIGCHLD, SIG_DFL);
  93 #endif
  94 }
  95
  96
  97 /* Create a subprocess that is run as a filter.  ARGV is the
  98    NULL-terminated argument vector for the subprocess.  Store read and
  99    write file descriptors for communication with the subprocess into
 100    FD[0] and FD[1]: input meant for the process can be written into
 101    FD[0], and output from the process can be read from FD[1].  Return
 102    the subprocess id.
 103
 104    To avoid deadlock, the invoker must not let incoming data pile up
 105    in FD[1] while writing data to FD[0].  */
 106
 107 pid_t
 108 create_subpipe (char const * const *argv, int fd[2])
 109 {
 110   int pipe_fd[2];
 111   int child_fd[2];
 112   pid_t pid;
 113
 114   if (pipe_safer (child_fd) != 0 || pipe_safer (pipe_fd) != 0)
 115     error (EXIT_FAILURE, errno, "pipe");
 116   fd[0] = child_fd[1];
 117   fd[1] = pipe_fd[0];
 118   child_fd[1] = pipe_fd[1];
 119
 120   pid = vfork ();
 121   if (pid < 0)
 122     error (EXIT_FAILURE, errno, "fork");
 123
 124   if (! pid)
 125     {
 126       /* Child.  */
 127       close (fd[0]);
 128       close (fd[1]);
 129       dup2 (child_fd[0], STDIN_FILENO);
 130       close (child_fd[0]);
 131       dup2 (child_fd[1], STDOUT_FILENO);
 132       close (child_fd[1]);
 133
 134       /* The cast to (char **) rather than (char * const *) is needed
 135          for portability to older hosts with a nonstandard prototype
 136          for execvp.  */
 137       execvp (argv[0], (char **) argv);
 138
 139       _exit (errno == ENOENT ? 127 : 126);
 140     }
 141
 142   /* Parent.  */
 143   close (child_fd[0]);
 144   close (child_fd[1]);
 145   return pid;
 146 }
 147
 148
 149 /* Wait for the subprocess to exit.  */
 150
 151 void
 152 reap_subpipe (pid_t pid, char const *program)
 153 {
 154 #if HAVE_WAITPID || defined waitpid
 155   int wstatus;
 156   if (waitpid (pid, &wstatus, 0) < 0)
 157     error (EXIT_FAILURE, errno, "waitpid");
 158   else
 159     {
 160       int status = WIFEXITED (wstatus) ? WEXITSTATUS (wstatus) : -1;
 161       if (status)
 162         error (EXIT_FAILURE, 0,
 163                _(status == 126
 164                  ? "subsidiary program `%s' could not be invoked"
 165                  : status == 127
 166                  ? "subsidiary program `%s' not found"
 167                  : status < 0
 168                  ? "subsidiary program `%s' failed"
 169                  : "subsidiary program `%s' failed (exit status %d)"),
 170                program, status);
 171     }
 172 #endif
 173 }
 174
 175 void
 176 end_of_output_subpipe (pid_t pid ATTRIBUTE_UNUSED,
 177                        int fd[2] ATTRIBUTE_UNUSED)
 178 {
 179 }