#include <stdio.h>#include <errno.h>#include <unistd.h>#include <fcntl.h>int main(int argc,char* argv[]){	int fd;	int lock_result;	struct flock lock;		if(argc!=2){		printf("Usage: %s lock_file_name\n",argv[0]);		return 1;	}		fd=open(argv[1],O_RDWR);	if(fd<0){		perror("cannot open the file");		return 1;	}	lock_result=lockf(fd,F_LOCK,0);		if(lock_result==-1){		perror("cannot get the lock....");		return 0;	}	printf("pid: %ld process lock the file\n",(long)getpid());	sleep(1);	printf("pid: %ld process release the file\n",(long)getpid());	return 0;}