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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
|
