I'm trying to use fcntl lib (at UNIX c programming) to lock or unlock files but seems isn't lock and I don't know why. I don't receive any error, it looks like that the program doing the lock but actually i can read/write the file and isn't locked
if (enter == 2){
getchar ();
int fd;
struct flock lock;
char file[20];
printf ("Enter file name:");
fgets(file,20,stdin);
printf ("opening %s\n", file);
//Open a file descriptor to the file
fd = open (file, O_RDWR);
printf ("locking\n");
//Initialize the flock structure
memset (&lock, 0, sizeof(lock));
lock.l_type = F_WRLCK;
//Place a write lock on the file
fcntl (fd, F_SETLK, &lock);
printf ("locked; hit Enter to unlock... ");
//Wait for the user to hit Enter
getchar ();
printf ("unlocking\n");
//Release the lock
lock.l_type = F_UNLCK;
fcntl (fd, F_SETLK, &lock);
close (fd);
It's very bold of you to claim you have locked the file when you didn't check the result of fcntl.
Anyway, that is the expected behaviour. All getting a lock does is prevent others from getting a lock.[1] It doesn't prevent anyone from reading from or writing to the file.