#include <stdio.h>
#include <sys/file.h>
#include <fcntl.h>

/** flockdemo.c - shows how to lock an entire file        **/
/** usage: flockdemo filename {shared|exclusive|nonblock} **/

main(int ac, char *av[])
{
	int	rv;
	int	fd;
	int	operation;

	if ( ac != 3 ){
		fprintf(stderr,"usage: flockdemo file {s|e|n}\n");
		exit(1);
	}

	if      ( *av[2] == 's' ) operation = LOCK_SH;
	else if ( *av[2] == 'e' ) operation = LOCK_EX;
	else if ( *av[2] == 'n' ) operation = LOCK_NB;

	if ( ( fd = open(av[1],O_RDWR)) == -1 )
		perror(av[1]);
	else {
		rv = flock(fd, operation);
		printf("flock returned %d. Press return..", rv);
		getchar();
	}
}