setlock - runs another program with a file locked.

fn is a single argument.  child consists of one or more arguments.

       setlock  opens  fn  for  writing (creating it if it does not exist), obtains an exclusive lock on it, and
       runs child.

       Normally the lock disappears when child exits.

       Here's the complete story: child is given a descriptor for a locked ofile pointing to the disk file named
       fn.  The lock disappears when this ofile is

       o      closed by all the processes that have descriptors for it or

       o      explicitly unlocked.

       setlock - runs another program with a file locked.

-n     No delay. If fn is locked by another process, setlock gives up.

       -N     (Default.) Delay. If fn is locked by another process, setlock waits until  it  can  obtain  a  new
              lock.

       -x     If fn cannot be opened (or created) or locked, setlock exits zero.

       -X     (Default.)  If  fn  cannot  be  opened (or created) or locked, setlock prints an error message and
              exits nonzero.

supervise(8),  svc(8),  svok(8),  svstat(8),  svscanboot(8),  svscan(8),   readproctitle(8),   fghack(8),
       pgrphack(8), multilog(8), tai64n(8), tai64nlocal(8), setuidgid(8), envuidgid(8), envdir(8), softlimit(8)

       http://cr.yp.to/daemontools.htmlsetlock(8)

setlock [ -nNxX ] fnchild