lib/subpipe.c

   1 /* Subprocesses with pipes.
   2
   3    Copyright (C) 2002, 2004, 2005, 2006, 2009 Free Software Foundation,
   4    Inc.
   5
   6    This program is free software: you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation, either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  18
  19 /* Written by Paul Eggert <eggert@twinsun.com>
  20    and Florian Krohm <florian@edamail.fishkill.ibm.com>.  */
  21
  22 #include <config.h>
  23
  24 #include "subpipe.h"
  25
  26 #include <errno.h>
  27
  28 #include <signal.h>
  29 #if ! defined SIGCHLD && defined SIGCLD
  30 # define SIGCHLD SIGCLD
  31 #endif
  32
  33 #include <stdlib.h>
  34
  35 #include <unistd.h>
  36 #ifndef STDIN_FILENO
  37 # define STDIN_FILENO 0
  38 #endif
  39 #ifndef STDOUT_FILENO
  40 # define STDOUT_FILENO 1
  41 #endif
  42 #if ! HAVE_DUP2 && ! defined dup2
  43 # include <fcntl.h>
  44 # define dup2(f, t) (close (t), fcntl (f, F_DUPFD, t))
  45 #endif
  46
  47 #if HAVE_SYS_WAIT_H
  48 # include <sys/wait.h>
  49 #endif
  50 #ifndef WEXITSTATUS
  51 # define WEXITSTATUS(stat_val) ((unsigned int) (stat_val) >> 8)
  52 #endif
  53 #ifndef WIFEXITED
  54 # define WIFEXITED(stat_val) (((stat_val) & 255) == 0)
  55 #endif
  56
  57 #if HAVE_VFORK_H
  58 # include <vfork.h>
  59 #endif
  60 #if ! HAVE_WORKING_VFORK
  61 # define vfork fork
  62 #endif
  63
  64 #include "error.h"
  65 #include "unistd-safer.h"
  66
  67 #include "gettext.h"
  68 #define _(Msgid)  gettext (Msgid)
  69
  70 #ifndef __attribute__
  71 /* This feature is available in gcc versions 2.5 and later.  */
  72 # if ! defined __GNUC__ || __GNUC__ < 2 || \
  73 (__GNUC__ == 2 && __GNUC_MINOR__ < 5) || __STRICT_ANSI__
  74 #  define __attribute__(Spec) /* empty */
  75 # endif
  76 #endif
  77
  78 #ifndef ATTRIBUTE_UNUSED
  79 # define ATTRIBUTE_UNUSED __attribute__ ((__unused__))
  80 #endif
  81
  82
  83 /* Initialize this module.  */
  84
  85 void
  86 init_subpipe (void)
  87 {
  88 #ifdef SIGCHLD
  89   /* System V fork+wait does not work if SIGCHLD is ignored.  */
  90   signal (SIGCHLD, SIG_DFL);
  91 #endif
  92 }
  93
  94
  95 /* Create a subprocess that is run as a filter.  ARGV is the
  96    NULL-terminated argument vector for the subprocess.  Store read and
  97    write file descriptors for communication with the subprocess into
  98    FD[0] and FD[1]: input meant for the process can be written into
  99    FD[0], and output from the process can be read from FD[1].  Return
 100    the subprocess id.
 101
 102    To avoid deadlock, the invoker must not let incoming data pile up
 103    in FD[1] while writing data to FD[0].  */
 104
 105 pid_t
 106 create_subpipe (char const * const *argv, int fd[2])
 107 {
 108   int pipe_fd[2];
 109   int child_fd[2];
 110   pid_t pid;
 111
 112   if (pipe_safer (child_fd) != 0 || pipe_safer (pipe_fd) != 0)
 113     error (EXIT_FAILURE, errno, "pipe");
 114   fd[0] = child_fd[1];
 115   fd[1] = pipe_fd[0];
 116   child_fd[1] = 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 (fd[0]);
 126       close (fd[1]);
 127       dup2 (child_fd[0], STDIN_FILENO);
 128       close (child_fd[0]);
 129       dup2 (child_fd[1], STDOUT_FILENO);
 130       close (child_fd[1]);
 131
 132       /* The cast to (char **) rather than (char * const *) is needed
 133          for portability to older hosts with a nonstandard prototype
 134          for execvp.  */
 135       execvp (argv[0], (char **) argv);
 136
 137       _exit (errno == ENOENT ? 127 : 126);
 138     }
 139
 140   /* Parent.  */
 141   close (child_fd[0]);
 142   close (child_fd[1]);
 143   return pid;
 144 }
 145
 146
 147 /* Wait for the subprocess to exit.  */
 148
 149 void
 150 reap_subpipe (pid_t pid, char const *program)
 151 {
 152 #if HAVE_WAITPID || defined waitpid
 153   int wstatus;
 154   if (waitpid (pid, &wstatus, 0) < 0)
 155     error (EXIT_FAILURE, errno, "waitpid");
 156   else
 157     {
 158       int status = WIFEXITED (wstatus) ? WEXITSTATUS (wstatus) : -1;
 159       if (status)
 160         error (EXIT_FAILURE, 0,
 161                _(status == 126
 162                  ? "subsidiary program `%s' could not be invoked"
 163                  : status == 127
 164                  ? "subsidiary program `%s' not found"
 165                  : status < 0
 166                  ? "subsidiary program `%s' failed"
 167                  : "subsidiary program `%s' failed (exit status %d)"),
 168                program, status);
 169     }
 170 #endif
 171 }
 172
 173 void
 174 end_of_output_subpipe (pid_t pid ATTRIBUTE_UNUSED,
 175                        int fd[2] ATTRIBUTE_UNUSED)
 176 {
 177 }