179 lines
3.8 KiB
C
179 lines
3.8 KiB
C
/*
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FUNCTION
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<<system>>---execute command string
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INDEX
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system
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INDEX
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_system_r
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SYNOPSIS
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#include <stdlib.h>
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int system(char *<[s]>);
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int _system_r(void *<[reent]>, char *<[s]>);
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DESCRIPTION
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Use <<system>> to pass a command string <<*<[s]>>> to <</bin/sh>> on
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your system, and wait for it to finish executing.
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Use ``<<system(NULL)>>'' to test whether your system has <</bin/sh>>
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available.
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The alternate function <<_system_r>> is a reentrant version. The
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extra argument <[reent]> is a pointer to a reentrancy structure.
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RETURNS
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<<system(NULL)>> returns a non-zero value if <</bin/sh>> is available, and
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<<0>> if it is not.
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With a command argument, the result of <<system>> is the exit status
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returned by <</bin/sh>>.
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PORTABILITY
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ANSI C requires <<system>>, but leaves the nature and effects of a
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command processor undefined. ANSI C does, however, specify that
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<<system(NULL)>> return zero or nonzero to report on the existence of
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a command processor.
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POSIX.2 requires <<system>>, and requires that it invoke a <<sh>>.
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Where <<sh>> is found is left unspecified.
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Supporting OS subroutines required: <<_exit>>, <<_execve>>, <<_fork_r>>,
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<<_wait_r>>.
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*/
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#include <_ansi.h>
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#include <errno.h>
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#include <stddef.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <_syslist.h>
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#include <reent.h>
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#if defined (unix) || defined (__CYGWIN__)
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static int do_system (struct _reent *ptr, const char *s);
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#endif
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int
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_system_r (struct _reent *ptr,
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const char *s)
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{
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#if defined(HAVE_SYSTEM)
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return _system (s);
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ptr = ptr;
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#elif defined(NO_EXEC)
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if (s == NULL)
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return 0;
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errno = ENOSYS;
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return -1;
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#else
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/* ??? How to handle (s == NULL) here is not exactly clear.
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If _fork_r fails, that's not really a justification for returning 0.
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For now we always return 0 and leave it to each target to explicitly
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handle otherwise (this can always be relaxed in the future). */
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#if defined (unix) || defined (__CYGWIN__)
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if (s == NULL)
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return 1;
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return do_system (ptr, s);
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#else
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if (s == NULL)
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return 0;
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errno = ENOSYS;
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return -1;
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#endif
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#endif
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}
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#ifndef _REENT_ONLY
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int
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system (const char *s)
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{
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return _system_r (_REENT, s);
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}
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#endif
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#if defined (unix) && !defined (__CYGWIN__) && !defined(__rtems__)
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extern char **environ;
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/* Only deal with a pointer to environ, to work around subtle bugs with shared
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libraries and/or small data systems where the user declares his own
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'environ'. */
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static char ***p_environ = &environ;
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static int
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do_system (struct _reent *ptr,
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const char *s)
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{
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char *argv[4];
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int pid, status;
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argv[0] = "sh";
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argv[1] = "-c";
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argv[2] = (char *) s;
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argv[3] = NULL;
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if ((pid = _fork_r (ptr)) == 0)
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{
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_execve ("/bin/sh", argv, *p_environ);
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exit (100);
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}
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else if (pid == -1)
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return -1;
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else
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{
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int rc = _wait_r (ptr, &status);
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if (rc == -1)
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return -1;
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status = (status >> 8) & 0xff;
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return status;
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}
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}
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#endif
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#if defined (__CYGWIN__)
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static int
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do_system (struct _reent *ptr,
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const char *s)
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{
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char *argv[4];
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int pid, status;
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argv[0] = "sh";
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argv[1] = "-c";
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argv[2] = (char *) s;
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argv[3] = NULL;
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if ((pid = vfork ()) == 0)
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{
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/* ??? It's not clear what's the right path to take (pun intended :-).
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There won't be an "sh" in any fixed location so we need each user
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to be able to say where to find "sh". That suggests using an
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environment variable, but after a few more such situations we may
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have too many of them. */
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char *sh = getenv ("SH_PATH");
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if (sh == NULL)
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sh = "/bin/sh";
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_execve (sh, argv, environ);
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exit (100);
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}
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else if (pid == -1)
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return -1;
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else
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{
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extern int _wait (int *);
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int rc = _wait (&status);
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if (rc == -1)
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return -1;
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status = (status >> 8) & 0xff;
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return status;
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}
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}
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#endif
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