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/*
Copyright (c) 1990 Regents of the University of California.
All rights reserved.
*/
/*
FUNCTION
<<system>>---execute command string
INDEX
system
INDEX
_system_r
SYNOPSIS
#include <stdlib.h>
int system(char *<[s]>);
int _system_r(void *<[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 <sys/wait.h>
#if defined(unix) || defined(__CYGWIN__)
static int do_system(const char *s);
#endif
int
system(const char *s)
{
#if defined(HAVE_SYSTEM)
return _system(s);
#elif defined(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(s);
#else
if (s == NULL)
return 0;
errno = ENOSYS;
return -1;
#endif
#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(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()) == 0) {
execve("/bin/sh", argv, *p_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
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