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

int main(int argc, char **argv)
{
   int lockStatus,
       fd;
   
   if ( (fd = open(argv[1], O_RDWR)) <0)
   {
   	printf("opening file %s failed\n",argv[1]);
	exit(1);
   } //if
   
   lockStatus = lockf(fd, F_TEST, 0L);
     
   switch(errno)
   {
	case (0):
	   printf("file is unlocked\n");
	   break;
   	case (EACCES):
	case (EAGAIN):
	   printf("file is already locked\n");
   } //switch
   
   return(0);
} //main()