C > Gnu-Linux

Fcntl, locking files

Fcntl, locking files

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

#define PACKAGE "crlock"

int main(void) {
 int fd = 0;
 int i = 5;

 for(; i > 0; i--) {
  if((fd = open("locked.file", O_RDWR|O_CREAT|O_EXCL, 0444)) == -1) {
   fprintf(stderr, "%s [%d]: Error - file already locked ...\n", PACKAGE, getpid());
   sleep(1);
  } else {
   fprintf(stdout, "%s [%d]: Now I am the only one with access :-)\n", 
     PACKAGE, getpid());

   sleep(1);
   close(fd);
   unlink("locked.file");
   sleep(1);
  } /* else */
 } /* while */

 return 0;
}