Updated: 2021/Apr/14

FLOCK(1)                    General Commands Manual                   FLOCK(1)

     flock - Provide locking API for shell scripts

     flock [-dnosvx] [-w timeout] file|directory command [args ...]
     flock [-dnosvx] [-w timeout] file|directory -c command
     flock [-dnsuvx] [-w timeout] number

     The flock utility provides flock(2) access to the command line or
     scripts.  The first two forms lock the specified file or directory while
     the provided command is executed.  If the path does not exist, then a
     file of that name is created with mode 0600.

     The third form can use an arbitrary file descriptor number that is
     provided from a shell script for example:

                   flock -s 100
                   # commands to be executed under the lock
           ) 100> /path/to/lockfile

     The following options are available:

     -c command  Pass a command to a the shell.

     -d, --debug
                 Provide debugging output.

     -n, --nb, --nonblock
                 Don't block and fail immediately if the lock could not be

     -o, --close
                 Close the file before executing the command.  This is useful
                 if the child forks and should not be holding the lock.

     -s, --shared
                 Obtain a shared lock.

     -u, --unlock
                 Unlock an existing lock.  This is available only for a file

     -v, --verbose
                 On error print an explanation of the failure.

     -w, --wait, --timeout seconds
                 Fail if the lock could not be obtained after seconds.

     -x, --exclusive
                 Obtain an exclusive lock.  This is the default.

     The flock utility exits 0 on success, and >0 if an error occurs.

     shlock(1), flock(2)

     An flock utility appeared in NetBSD 6.1.

NetBSD 9.99                     October 4, 2019                    NetBSD 9.99