sysdeps/posix/system.c

   1 /* Copyright (C) 1991, 92, 94, 95, 96, 97 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 not,
  16    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, 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     /* This signals that we have a command processor available.  */
  48     return 1;
  49
  50   sa.sa_handler = SIG_IGN;
  51   sa.sa_flags = 0;
  52   __sigemptyset (&sa.sa_mask);
  53
  54   if (__sigaction (SIGINT, &sa, &intr) < 0)
  55     return -1;
  56   if (__sigaction (SIGQUIT, &sa, &quit) < 0)
  57     {
  58       save = errno;
  59       (void) __sigaction (SIGINT, &intr, (struct sigaction *) NULL);
  60       __set_errno (save);
  61       return -1;
  62     }
  63
  64 #ifndef WAITPID_CANNOT_BLOCK_SIGCHLD
  65
  66 /* SCO 3.2v4 has a bug where `waitpid' will never return if SIGCHLD is
  67    blocked.  This makes it impossible for `system' to be implemented in
  68    compliance with POSIX.2-1992.  They have acknowledged that this is a bug
  69    but I have not seen nor heard of any forthcoming fix.  */
  70
  71   __sigemptyset (&block);
  72   __sigaddset (&block, SIGCHLD);
  73   save = errno;
  74   if (__sigprocmask (SIG_BLOCK, &block, &omask) < 0)
  75     {
  76       if (errno == ENOSYS)
  77         __set_errno (save);
  78       else
  79         {
  80           save = errno;
  81           (void) __sigaction (SIGINT, &intr, (struct sigaction *) NULL);
  82           (void) __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL);
  83           __set_errno (save);
  84           return -1;
  85         }
  86     }
  87 #define UNBLOCK __sigprocmask (SIG_SETMASK, &omask, (sigset_t *) NULL)
  88 #else
  89 #define UNBLOCK 0
  90 #endif
  91
  92   pid = __vfork ();
  93   if (pid == (pid_t) 0)
  94     {
  95       /* Child side.  */
  96       const char *new_argv[4];
  97       new_argv[0] = SHELL_NAME;
  98       new_argv[1] = "-c";
  99       new_argv[2] = line;
 100       new_argv[3] = NULL;
 101
 102       /* Restore the signals.  */
 103       (void) __sigaction (SIGINT, &intr, (struct sigaction *) NULL);
 104       (void) __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL);
 105       (void) UNBLOCK;
 106
 107       /* Exec the shell.  */
 108       (void) __execve (SHELL_PATH, (char *const *) new_argv, __environ);
 109       _exit (127);
 110     }
 111   else if (pid < (pid_t) 0)
 112     /* The fork failed.  */
 113     status = -1;
 114   else
 115     /* Parent side.  */
 116 #ifdef  NO_WAITPID
 117     {
 118       pid_t child;
 119       do
 120         {
 121           child = __wait (&status);
 122           if (child <= -1)
 123             {
 124               status = -1;
 125               break;
 126             }
 127         } while (child != pid);
 128     }
 129 #else
 130     if (__waitpid (pid, &status, 0) != pid)
 131       status = -1;
 132 #endif
 133
 134   save = errno;
 135   if ((__sigaction (SIGINT, &intr, (struct sigaction *) NULL) |
 136        __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL) |
 137        UNBLOCK) != 0)
 138     {
 139       if (errno == ENOSYS)
 140         __set_errno (save);
 141       else
 142         return -1;
 143     }
 144
 145   return status;
 146 }
 147 weak_alias (__libc_system, system)