flock

Run command with file lock

$ flock /tmp/lock.lock command

$ flock -n /tmp/lock.lock command

$ flock -w 10 /tmp/lock.lock command

$ flock -n -E 42 /tmp/lock.lock command

$ flock /tmp/lock.lock -c "command1 && command2"

$ flock -s /tmp/lock.lock command

flock [options] file|directory command [arguments]
flock [options] file|directory -c command
flock [options] number

flock manages file locks from shell scripts. It executes a command while holding a lock on a specified file or directory, creating the lock file if needed. By default, the command waits indefinitely for the lock to become available. This is useful for ensuring only one instance of a command runs at a time.

-c, --command

Execute a single command string via the shell

Obtain an exclusive (write) lock (default)

Obtain a shared (read) lock

Fail immediately if the lock is not available

Fail if the lock is not acquired within specified seconds

Close the file descriptor before executing the command

Manually drop the lock

Exit code when lock fails with -n or timeout (default: 1)

Do not fork before executing the command

Report how long the lock took to acquire

flock does not detect deadlock situations. File locking has limited support on certain network filesystems like NFS and CIFS. When the -n or -w option is used and the lock cannot be acquired, flock exits with the code specified by -E (default 1).

flock is part of the util-linux package, providing shell-level access to the flock(2) system call.

flock(2), lockfile(1)