__fsetlocking - Linux


__fsetlocking is a powerful Linux command used to set file locking options. It allows fine-grained control over file locking behavior, providing robust data integrity and preventing concurrent access conflicts.


__fsetlocking [OPTIONS] FILE


  • -l: Lock the file.
  • -u: Unlock the file.
  • -s: Share the lock with other processes.
  • -e: Exclusive lock; prevent other processes from accessing the file.
  • -n: Non-blocking lock; return immediately with an error if the lock cannot be acquired.
  • -t: Timeout; wait for the specified number of seconds before returning with an error if the lock cannot be acquired.


Acquire an exclusive lock:

sudo __fsetlocking -e test.txt

Unlock the file:

sudo __fsetlocking -u test.txt

Share the lock with other processes:

sudo __fsetlocking -s test.txt

Non-blocking lock with a 5-second timeout:

sudo __fsetlocking -n -t 5 test.txt

Common Issues

  • Permission denied: Ensure that you have sufficient permissions to modify the file.
  • File already locked: Another process may have already locked the file. Try waiting or using the -n flag.
  • Invalid argument: Verify that you have specified valid options and arguments.


flock: Use __fsetlocking to control file locking in a script or command pipeline using the flock command.

Related Commands

  • lsof: List open files and their locks.
  • fsync: Flush data and metadata to disk.
  • chattr: Change file attributes, including locking.