system.c

/*
 * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
 *      The President and Fellows of Harvard College.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

/*
 * system(): ANSI C
 *
 * Run a command.
 */

#define MAXCMDSIZE 2048
#define MAXARGS    128

int
system(const char *cmd)
{
        /*
         * Ordinarily, you call the shell to process the command.
         * But we don't know that the shell can do that. So, do it
         * ourselves.
         */

        char tmp[MAXCMDSIZE];
        char *argv[MAXARGS+1];
        int nargs=0;
        char *s;
        int pid, status;

        if (strlen(cmd) >= sizeof(tmp)) {
                errno = E2BIG;
                return -1;
        }
        strcpy(tmp, cmd);

        for (s = strtok(tmp, " \t"); s; s = strtok(NULL, " \t")) {
                if (nargs < MAXARGS) {
                        argv[nargs++] = s;
                }
                else {
                        errno = E2BIG;
                        return 1;
                }
        }

        argv[nargs] = NULL;

        pid = fork();
        switch (pid) {
            case -1:
                return -1;
            case 0:
                /* child */
                execv(argv[0], argv);
                /* exec only returns if it fails */
                _exit(255);
            default:
                /* parent */
                waitpid(pid, &status, 0);
                return status;
        }
}