/*************************************************************************\
*                  Copyright (C) Michael Kerrisk, 2026.                   *
*                                                                         *
* This program is free software. You may use, modify, and redistribute it *
* under the terms of the GNU General Public License as published by the   *
* Free Software Foundation, either version 3 or (at your option) any      *
* later version. This program is distributed without any warranty.  See   *
* the file COPYING.gpl-v3 for details.                                    *
\*************************************************************************/

/* vfork_fd_test.c

   Demonstrate that a vfork()ed child has a separate set of file descriptors
   from its parent.
*/
#define _BSD_SOURCE     /* To get vfork() declaration from <unistd.h>
                           in case _XOPEN_SOURCE >= 700 */
#include "tlpi_hdr.h"

int
main(int argc, char *argv[])
{
    switch (vfork()) {
    case -1: errExit("vfork");

    case 0: if (close(STDOUT_FILENO) == -1)
                errMsg("close - child");
            _exit(EXIT_SUCCESS);

    default: break;
    }

    /* Now parent closes STDOUT_FILENO twice: only the second close
       should fail, indicating that the close(STDOUT_FILENO) by the
       child did not affect the parent. */

    if (close(STDOUT_FILENO) == -1)
        errMsg("close");
    if (close(STDOUT_FILENO) == -1)
        errMsg("close");

    exit(EXIT_SUCCESS);
}