source: trunk/minix/lib/ansi/system.c@ 20

/*
 * (c) copyright 1987 by the Vrije Universiteit, Amsterdam, The Netherlands.
 * See the copyright notice in the ACK home directory, in the file "Copyright".
 */
/* $Header: /cvsup/minix/src/lib/ansi/system.c,v 1.1.1.1 2005/04/21 14:56:06 beng Exp $ */

#if     defined(_POSIX_SOURCE)
#include        <sys/types.h>
#endif
#include        <stdlib.h>
#include        <signal.h>

extern pid_t _fork(void);
extern pid_t _wait(int *);
extern void _exit(int);
extern void _execve(const char *path, const char ** argv, const char ** envp);
extern int _close(int);

#define FAIL    127

extern const char ***_penviron;
static const char *exec_tab[] = {
        "sh",                   /* argv[0] */
        "-c",                   /* argument to the shell */
        NULL,                   /* to be filled with user command */
        NULL                    /* terminating NULL */
        };

int
system(const char *str)
{
        int pid, exitstatus, waitval;
        int i;

        if ((pid = _fork()) < 0) return str ? -1 : 0;

        if (pid == 0) {
                for (i = 3; i <= 20; i++)
                        _close(i);
                if (!str) str = "cd .";         /* just testing for a shell */
                exec_tab[2] = str;              /* fill in command */
                _execve("/bin/sh", exec_tab, *_penviron);
                /* get here if execve fails ... */
                _exit(FAIL);    /* see manual page */
        }
        while ((waitval = _wait(&exitstatus)) != pid) {
                if (waitval == -1) break;
        }
        if (waitval == -1) {
                /* no child ??? or maybe interrupted ??? */
                exitstatus = -1;
        }
        if (!str) {
                if (exitstatus == FAIL << 8)            /* execve() failed */
                        exitstatus = 0;
                else exitstatus = 1;                    /* /bin/sh exists */
        }
        return exitstatus;
}