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 3 of the License, or
   8    (at your option) 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, see <http://www.gnu.org/licenses/>.  */
  17
  18 /* Written by Paul Eggert <eggert@twinsun.com>
  19    and Florian Krohm <florian@edamail.fishkill.ibm.com>.  */
  20
  21 #include <config.h>
  22
  23 #include "subpipe.h"
  24
  25 #include <errno.h>
  26
  27 #include <signal.h>
  28 #if ! defined SIGCHLD && defined SIGCLD
  29 # define SIGCHLD SIGCLD
  30 #endif
  31
  32 #include <stdlib.h>
  33
  34 #include <unistd.h>
  35 #ifndef STDIN_FILENO
  36 # define STDIN_FILENO 0
  37 #endif
  38 #ifndef STDOUT_FILENO
  39 # define STDOUT_FILENO 1
  40 #endif
  41 #if ! HAVE_DUP2 && ! defined dup2
  42 # include <fcntl.h>
  43 # define dup2(f, t) (close (t), fcntl (f, F_DUPFD, t))
  44 #endif
  45
  46 #if HAVE_SYS_WAIT_H
  47 # include <sys/wait.h>
  48 #endif
  49 #ifndef WEXITSTATUS
  50 # define WEXITSTATUS(stat_val) ((unsigned int) (stat_val) >> 8)
  51 #endif
  52 #ifndef WIFEXITED
  53 # define WIFEXITED(stat_val) (((stat_val) & 255) == 0)
  54 #endif
  55
  56 #if HAVE_VFORK_H
  57 # include <vfork.h>
  58 #endif
  59 #if ! HAVE_WORKING_VFORK
  60 # define vfork fork
  61 #endif
  62
  63 #include "error.h"
  64 #include "unistd-safer.h"
  65
  66 #include "gettext.h"
  67 #define _(Msgid)  gettext (Msgid)
  68
  69 #ifndef __attribute__
  70 /* This feature is available in gcc versions 2.5 and later.  */
  71 # if ! defined __GNUC__ || __GNUC__ < 2 || \
  72 (__GNUC__ == 2 && __GNUC_MINOR__ < 5) || __STRICT_ANSI__
  73 #  define __attribute__(Spec) /* empty */
  74 # endif
  75 #endif
  76
  77 #ifndef ATTRIBUTE_UNUSED
  78 # define ATTRIBUTE_UNUSED __attribute__ ((__unused__))
  79 #endif
  80
  81
  82 /* Initialize this module.  */
  83
  84 void
  85 init_subpipe (void)
  86 {
  87 #ifdef SIGCHLD
  88   /* System V fork+wait does not work if SIGCHLD is ignored.  */
  89   signal (SIGCHLD, SIG_DFL);
  90 #endif
  91 }
  92
  93
  94 /* Create a subprocess that is run as a filter.  ARGV is the
  95    NULL-terminated argument vector for the subprocess.  Store read and
  96    write file descriptors for communication with the subprocess into
  97    FD[0] and FD[1]: input meant for the process can be written into
  98    FD[0], and output from the process can be read from FD[1].  Return
  99    the subprocess id.
 100
 101    To avoid deadlock, the invoker must not let incoming data pile up
 102    in FD[1] while writing data to FD[0].  */
 103
 104 pid_t
 105 create_subpipe (char const * const *argv, int fd[2])
 106 {
 107   int pipe_fd[2];
 108   int child_fd[2];
 109   pid_t pid;
 110
 111   if (pipe_safer (child_fd) != 0 || pipe_safer (pipe_fd) != 0)
 112     error (EXIT_FAILURE, errno, "pipe");
 113   fd[0] = child_fd[1];
 114   fd[1] = pipe_fd[0];
 115   child_fd[1] = pipe_fd[1];
 116
 117   pid = vfork ();
 118   if (pid < 0)
 119     error (EXIT_FAILURE, errno, "fork");
 120
 121   if (! pid)
 122     {
 123       /* Child.  */
 124       close (fd[0]);
 125       close (fd[1]);
 126       dup2 (child_fd[0], STDIN_FILENO);
 127       close (child_fd[0]);
 128       dup2 (child_fd[1], STDOUT_FILENO);
 129       close (child_fd[1]);
 130
 131       /* The cast to (char **) rather than (char * const *) is needed
 132          for portability to older hosts with a nonstandard prototype
 133          for execvp.  */
 134       execvp (argv[0], (char **) argv);
 135
 136       _exit (errno == ENOENT ? 127 : 126);
 137     }
 138
 139   /* Parent.  */
 140   close (child_fd[0]);
 141   close (child_fd[1]);
 142   return pid;
 143 }
 144
 145
 146 /* Wait for the subprocess to exit.  */
 147
 148 void
 149 reap_subpipe (pid_t pid, char const *program)
 150 {
 151 #if HAVE_WAITPID || defined waitpid
 152   int wstatus;
 153   if (waitpid (pid, &wstatus, 0) < 0)
 154     error (EXIT_FAILURE, errno, "waitpid");
 155   else
 156     {
 157       int status = WIFEXITED (wstatus) ? WEXITSTATUS (wstatus) : -1;
 158       if (status)
 159         error (EXIT_FAILURE, 0,
 160                _(status == 126
 161                  ? "subsidiary program `%s' could not be invoked"
 162                  : status == 127
 163                  ? "subsidiary program `%s' not found"
 164                  : status < 0
 165                  ? "subsidiary program `%s' failed"
 166                  : "subsidiary program `%s' failed (exit status %d)"),
 167                program, status);
 168     }
 169 #endif
 170 }
 171
 172 void
 173 end_of_output_subpipe (pid_t pid ATTRIBUTE_UNUSED,
 174                        int fd[2] ATTRIBUTE_UNUSED)
 175 {
 176 }