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/*

FUNCTION

<<system>>---execute command string

INDEX

        system

INDEX

        _system_r

ANSI_SYNOPSIS

        #include <stdlib.h>

        int system(char *<[s]>);

        int _system_r(void *<[reent]>, char *<[s]>);

TRAD_SYNOPSIS

        #include <stdlib.h>

        int system(<[s]>)

        char *<[s]>;

        int _system_r(<[reent]>, <[s]>)

        char *<[reent]>;

        char *<[s]>;

DESCRIPTION

Use <<system>> to pass a command string <<*<[s]>>> to <</bin/sh>> on

your system, and wait for it to finish executing.

Use ``<<system(NULL)>>'' to test whether your system has <</bin/sh>>

available.

The alternate function <<_system_r>> is a reentrant version.  The

extra argument <[reent]> is a pointer to a reentrancy structure.

RETURNS

<<system(NULL)>> returns a non-zero value if <</bin/sh>> is available, and

<<0>> if it is not.

With a command argument, the result of <<system>> is the exit status

returned by <</bin/sh>>.

PORTABILITY

ANSI C requires <<system>>, but leaves the nature and effects of a

command processor undefined.  ANSI C does, however, specify that

<<system(NULL)>> return zero or nonzero to report on the existence of

a command processor.

POSIX.2 requires <<system>>, and requires that it invoke a <<sh>>.

Where <<sh>> is found is left unspecified.

Supporting OS subroutines required: <<_exit>>, <<_execve>>, <<_fork_r>>,

<<_wait_r>>.

*/

#include <errno.h>

#include <stddef.h>

#include <stdlib.h>

#include <unistd.h>

#include <_syslist.h>

#include <reent.h>

#if defined (unix) || defined (__CYGWIN__)

static int do_system ();

#endif

int

_system_r (ptr, s)

     struct _reent *ptr;

     _CONST char *s;

{

#ifdef NO_EXEC

  if (s == NULL)

    return 0;

  errno = ENOSYS;

  return -1;

#else

  /* ??? How to handle (s == NULL) here is not exactly clear.

     If _fork_r fails, that's not really a justification for returning 0.

     For now we always return 0 and leave it to each target to explicitly

     handle otherwise (this can always be relaxed in the future).  */

#if defined (unix) || defined (__CYGWIN__)

  if (s == NULL)

    return 1;

  return do_system (ptr, s);

#else

  if (s == NULL)

    return 0;

  errno = ENOSYS;

  return -1;

#endif

#endif

}

#ifndef _REENT_ONLY

int

system (s)

     _CONST char *s;

{

  return _system_r (_REENT, s);

}

#endif

#if defined (unix) && !defined (__CYGWIN__) && !defined(__rtems__)

extern char **environ;

/* Only deal with a pointer to environ, to work around subtle bugs with shared

   libraries and/or small data systems where the user declares his own

   'environ'.  */

static char ***p_environ = &environ;

static int

do_system (ptr, s)

     struct _reent *ptr;

     _CONST char *s;

{

  char *argv[4];

  int pid, status;

  argv[0] = "sh";

  argv[1] = "-c";

  argv[2] = (char *) s;

  argv[3] = NULL;

  if ((pid = _fork_r (ptr)) == 0)

    {

      _execve ("/bin/sh", argv, *p_environ);

      exit (100);

    }

  else if (pid == -1)

    return -1;

  else

    {

      int rc = _wait_r (ptr, &status);

      if (rc == -1)

        return -1;

      status = (status >> 8) & 0xff;

      return status;

    }

}

#endif

#if defined (__CYGWIN__)

static int

do_system (ptr, s)

     struct _reent *ptr;

     _CONST char *s;

{

  char *argv[4];

  int pid, status;

  argv[0] = "sh";

  argv[1] = "-c";

  argv[2] = (char *) s;

  argv[3] = NULL;

  if ((pid = vfork ()) == 0)

    {

      /* ??? It's not clear what's the right path to take (pun intended :-).

         There won't be an "sh" in any fixed location so we need each user

         to be able to say where to find "sh".  That suggests using an

         environment variable, but after a few more such situations we may

         have too many of them.  */

      char *sh = getenv ("SH_PATH");

      if (sh == NULL)

        sh = "/bin/sh";

      _execve (sh, argv, environ);

      exit (100);

    }

  else if (pid == -1)

    return -1;

  else

    {

      int rc = _wait (&status);

      if (rc == -1)

        return -1;

      status = (status >> 8) & 0xff;

      return status;

    }

}

#endif