/*
 * testlock - test if a fle has been flocked
 *
 * usage:
 *	testlock filename
 *
 *	filename	file to check if it is locked
 *
 * Exits with 0 if not locked (or file missing or not readable), 1 if locked.
 *
 * NOTE: In order to test locking, this must try to form a shared lock.
 * To be effective, the real locking process must obtain an exclusive
 * lock to deny this test.
 */
/*
 *
 * Copyright (C) 1997 Landon Curt Noll, all rights reserved.
 *
 * Permission to use, copy, modify, and distribute this software and
 * its documentation for any purpose is hereby granted, provided that
 * the above copyright, this permission notice, and the disclaimer
 * below appear in all of the following:
 *
 *         * supporting documentation
 *         * source copies
 *         * source works derived from this source
 *
 * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
 * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
 * USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
 * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 *
 * Landon Curt Noll <chongo was here> /\oo/\
 *
 * chongo@{toad,sgi}.com		Share and Enjoy!
 */

#include <stdio.h>
#include <sys/file.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>


main(int argc, char *argv[])
{
    int fd;		/* open file descriptor */
    char *filename;	/* filename to test */

    /*
     * parse args
     */
    if (argc != 2) {
	fprintf(stderr, "usage: %s filename\n", argv[0]);
	exit(0);
    }
    filename = argv[1];

    /*
     * open the file for reading
     */
    fd = open(filename, O_RDONLY);
    if (fd < 0) {
	fprintf(stderr, "%s: cannot open %s of reading\n", argv[0], filename);
	exit(0);
    }

    /*
     * check file for locking
     */
    errno = 0;
    if (flock(fd, LOCK_SH|LOCK_NB) < 0) {
	if (errno == EWOULDBLOCK) {
	    /* file was locked */
	    exit(1);
	} else {
	    fprintf(stderr, "%s: bad lock of %s\n", argv[0], filename);
	    exit(0);
	}
    }

    /* 
     * file was not locked but now is share locked ... until ...
     */
    /* close and unlock */
    close(fd);
    /* report that it was not locked */
    exit(0);
}