/*************************************************************************\
*                  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.                                    *
\*************************************************************************/

/* t_chown.c

   Demonstrate the use of the chown() system call to change the owner
   and group of a file.

   Usage: t_chown owner group [file...]

   Either or both of owner and/or group can be specified as "-" to
   leave them unchanged.
*/
#include <pwd.h>
#include <grp.h>
#include "ugid_functions.h"             /* Declarations of userIdFromName()
                                           and groupIdFromName() */
#include "tlpi_hdr.h"

int
main(int argc, char *argv[])
{
    uid_t uid;
    gid_t gid;
    int j;
    Boolean errFnd;

    if (argc < 3 || strcmp(argv[1], "--help") == 0)
        usageErr("%s owner group [file...]\n"
                "        owner or group can be '-', "
                "meaning leave unchanged\n", argv[0]);

    if (strcmp(argv[1], "-") == 0) {            /* "-" ==> don't change owner */
        uid = -1;
    } else {                                    /* Turn user name into UID */
        uid = userIdFromName(argv[1]);
        if (uid == (uid_t) -1)
            fatal("No such user (%s)", argv[1]);
    }

    if (strcmp(argv[2], "-") == 0) {            /* "-" ==> don't change group */
        gid = -1;
    } else {                                    /* Turn group name into GID */
        gid = groupIdFromName(argv[2]);
        if (gid == (gid_t) -1)
            fatal("No such group (%s)", argv[2]);
    }

    /* Change ownership of all files named in remaining arguments */

    errFnd = FALSE;
    for (j = 3; j < argc; j++) {
        if (chown(argv[j], uid, gid) == -1) {
            errMsg("chown: %s", argv[j]);
            errFnd = TRUE;
        }
    }

    exit(errFnd ? EXIT_FAILURE : EXIT_SUCCESS);
}