sysdeps/posix/system.c

   1 /* Copyright (C) 1991, 92, 94, 95, 96 Free Software Foundation, Inc.
   2 This file is part of the GNU C Library.
   3
   4 The GNU C Library is free software; you can redistribute it and/or
   5 modify it under the terms of the GNU Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 License, or (at your option) any later version.
   8
   9 The GNU C Library is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <stddef.h>
  20 #include <stdlib.h>
  21 #include <unistd.h>
  22 #include <sys/wait.h>
  23 #include <signal.h>
  24 #include <sys/types.h>
  25 #include <errno.h>
  26
  27
  28 #ifndef HAVE_GNU_LD
  29 #define __environ       environ
  30 #endif
  31
  32 #define SHELL_PATH      "/bin/sh"       /* Path of the shell.  */
  33 #define SHELL_NAME      "sh"            /* Name to give it.  */
  34
  35 /* Execute LINE as a shell command, returning its status.  */
  36 int
  37 __libc_system (const char *line)
  38 {
  39   int status, save;
  40   pid_t pid;
  41   struct sigaction sa, intr, quit;
  42 #ifndef WAITPID_CANNOT_BLOCK_SIGCHLD
  43   sigset_t block, omask;
  44 #endif
  45
  46   if (line == NULL)
  47     return 1;
  48
  49   sa.sa_handler = SIG_IGN;
  50   sa.sa_flags = 0;
  51   __sigemptyset (&sa.sa_mask);
  52
  53   if (__sigaction (SIGINT, &sa, &intr) < 0)
  54     return -1;
  55   if (__sigaction (SIGQUIT, &sa, &quit) < 0)
  56     {
  57       save = errno;
  58       (void) __sigaction (SIGINT, &intr, (struct sigaction *) NULL);
  59       __set_errno (save);
  60       return -1;
  61     }
  62
  63 #ifndef WAITPID_CANNOT_BLOCK_SIGCHLD
  64
  65 /* SCO 3.2v4 has a bug where `waitpid' will never return if SIGCHLD is
  66    blocked.  This makes it impossible for `system' to be implemented in
  67    compliance with POSIX.2-1992.  They have acknowledged that this is a bug
  68    but I have not seen nor heard of any forthcoming fix.  */
  69
  70   __sigemptyset (&block);
  71   __sigaddset (&block, SIGCHLD);
  72   save = errno;
  73   if (__sigprocmask (SIG_BLOCK, &block, &omask) < 0)
  74     {
  75       if (errno == ENOSYS)
  76         __set_errno (save);
  77       else
  78         {
  79           save = errno;
  80           (void) __sigaction (SIGINT, &intr, (struct sigaction *) NULL);
  81           (void) __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL);
  82           __set_errno (save);
  83           return -1;
  84         }
  85     }
  86 #define UNBLOCK __sigprocmask (SIG_SETMASK, &omask, (sigset_t *) NULL)
  87 #else
  88 #define UNBLOCK 0
  89 #endif
  90
  91   pid = __vfork ();
  92   if (pid == (pid_t) 0)
  93     {
  94       /* Child side.  */
  95       const char *new_argv[4];
  96       new_argv[0] = SHELL_NAME;
  97       new_argv[1] = "-c";
  98       new_argv[2] = line;
  99       new_argv[3] = NULL;
 100
 101       /* Restore the signals.  */
 102       (void) __sigaction (SIGINT, &intr, (struct sigaction *) NULL);
 103       (void) __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL);
 104       (void) UNBLOCK;
 105
 106       /* Exec the shell.  */
 107       (void) __execve (SHELL_PATH, (char *const *) new_argv, __environ);
 108       _exit (127);
 109     }
 110   else if (pid < (pid_t) 0)
 111     /* The fork failed.  */
 112     status = -1;
 113   else
 114     /* Parent side.  */
 115 #ifdef  NO_WAITPID
 116     {
 117       pid_t child;
 118       do
 119         {
 120           child = __wait (&status);
 121           if (child <= -1)
 122             {
 123               status = -1;
 124               break;
 125             }
 126         } while (child != pid);
 127     }
 128 #else
 129     if (__waitpid (pid, &status, 0) != pid)
 130       status = -1;
 131 #endif
 132
 133   save = errno;
 134   if ((__sigaction (SIGINT, &intr, (struct sigaction *) NULL) |
 135        __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL) |
 136        UNBLOCK) != 0)
 137     {
 138       if (errno == ENOSYS)
 139         __set_errno (save);
 140       else
 141         return -1;
 142     }
 143
 144   return status;
 145 }
 146 weak_alias (__libc_system, system)