lockfile-create

lockfile-progs(1) Lockfile programs lockfile-progs(1)

NAME

   lockfile-progs - command-line programs to safely lock and unlock files and mailboxes (via liblockfile).

SYNOPSIS

   mail-lock [--use-pid] [--retry retry-count]
   mail-unlock
   mail-touchlock [--oneshot]

   lockfile-create [--use-pid] [--retry retry-count] [--lock-name] filename
   lockfile-remove [--lock-name] filename
   lockfile-touch [--oneshot] [--lock-name] filename
   lockfile-check [--use-pid] [--lock-name] filename

DESCRIPTION

   Lockfile-progs provides a set a programs that can be used to lock and unlock mailboxes and files safely (via liblockfile):

       mail-lock - lock the current user's mailbox
       mail-unlock - unlock the current user's mailbox
       mail-touchlock - touch the lock on the current user's mailbox

       lockfile-create - lock a given file
       lockfile-remove - remove the lock on a given file
       lockfile-touch - touch the lock on a given file
       lockfile-check - check the lock on a given file

   By  default, the filename argument refers to the name of the file to be locked, and the name of the lockfile will be filename .lock.  However, if the --lock-
   name argument is specified, then filename will be taken as the name of the lockfile itself.

   Each of the mail locking commands attempts to lock /var/spool/mail/<user>, where <user> is the name associated with the effective user ID, as  determined  by
   via geteuid(2).

   Once a file is locked, the lock must be touched at least once every five minutes or the lock will be considered stale, and subsequent lock attempts will suc‐
   ceed.  Also see the --use-pid option and the lockfile_create(3) manpage.

   The lockfile-check command tests whether or not a valid lock already exists.

OPTIONS

   -q, --quiet
       Suppress any output.  Success or failure will only be indicated by the exit status.

   -v, --verbose
       Enable diagnostic output.

   -l, --lock-name
       Do not append .lock to the filename.  This option applies to lockfile-create, lockfile-remove, lockfile-touch, or lockfile-check.

   -p, --use-pid
       Write the parent process id (PPID) to the lockfile whenever a lockfile is created, and use that pid when checking  a  lock's  validity.   See  the  lock‐
       file_create(3)  manpage  for more information.  This option applies to lockfile-create and lockfile-check.  NOTE: this option will not work correctly be‐
       tween machines sharing a filesystem.

   -o, --oneshot
       Touch the lock and exit immediately.  This option applies to lockfile-touch and mail-touchlock.  When not provided,  these  commands  will  run  forever,
       touching the lock once every minute until killed.

   -r retry-count, --retry retry-count
       Try to lock filename retry-count times before giving up.  Each attempt will be delayed a bit longer than the last (in 5 second increments) until reaching
       a maximum delay of one minute between retries.  If retry-count is unspecified, the default is 9 which will give up after 225 seconds if all  9  lock  at‐
       tempts fail.

EXAMPLES

   Locking a file during a lengthy process:

     lockfile-create /some/file
     lockfile-touch /some/file &
     # Save the PID of the lockfile-touch process
     BADGER="$!"
     do-something-important-with /some/file
     kill "${BADGER}"
     lockfile-remove /some/file

EXIT STATUS

   0
       For lockfile-check this indicates that a valid lock exists, otherwise it just indicates successful program execution.

   Not 0
       For  lockfile-check  a  non-zero exit status indicates that the specified lock does not exist or is not valid.  For other programs it indicates that some
       problem was encountered.