lock2.c

BeginningLinuxProgramming example7

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <errno.h>

const char *lock_file = "/tmp/LCK.test2";

int main() {
    int file_desc;
    int tries = 10;

    while (tries--) {
        file_desc = open(lock_file, O_RDWR | O_CREAT | O_EXCL, 0444);
        if (file_desc == -1) {
            printf("%d - Lock already present\n", getpid());
            sleep(3);
        }
        else {
                /* critical region */
            printf("%d - I have exclusive access\n", getpid());
            sleep(1);
            (void)close(file_desc);
            (void)unlink(lock_file);
                /* non-critical region */
            sleep(2);
        }
    } /* while */
    exit(EXIT_SUCCESS);
}