Usage:
 flock [options] <file>|<directory> <command> [<argument>...]
 flock [options] <file>|<directory> -c <command>
 flock [options] <file descriptor number>

Manage file locks from shell scripts.

Options:
 -s, --shared             get a shared lock
 -x, --exclusive          get an exclusive lock (default)
 -u, --unlock             remove a lock
 -n, --nb, --nonblocking  fail rather than wait
 -w, --timeout <secs>     wait for a limited amount of time
 -E, --conflict-exit-code <number>  exit code after conflict or timeout
 -o, --close              close file descriptor before running command
 -c, --command <command>  run a single command string through the shell
 -F, --no-fork            execute command without forking
     --wait               same as --timeout
     --fcntl              use fcntl(F_OFD_SETLK) rather than flock()
     --start <offset>     starting offset for lock (implies --fcntl)
     --length <number>    number of bytes to lock (implies --fcntl)
     --verbose            increase verbosity

 -h, --help               display this help
 -V, --version            display version

For more details see flock(1).