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DOTLOCKFILE(1)				Cistron Utilities			   DOTLOCKFILE(1)

NAME
       dotlockfile - Utility to manage lockfiles

SYNOPSIS
       /usr/bin/dotlockfile [-p] [-c] [-m] [-l|-u|-t] [-r retries] [lockfile]

DESCRIPTION
       Dotlockfile  is	a command line utility to safely create, test and remove lockfiles. Lock-
       files are created in an NFS-safe way. Dotlockfile can can also be used to lock and  unlock
       mailboxes even if the mailspool directory is only writable by group mail.

       The  name dotlockfile comes from the way mailboxes are locked for updates on a lot of UNIX
       systems. A lockfile is created with the same filename as the mailbox but with  the  string
       ".lock" appended.

       The names dotlock and lockfile were already taken - hence the name dotlockfile :).

OPTIONS
       -l     Create a lockfile. This is the default.

       -u     Remove a lockfile.

       -c     Check for the existence of a valid lockfile.

       -t     Touch an existing lockfile (update the timestamp).

       -p     Write  the  process-id  of the calling process into the lockfile. Also when testing
	      for an existing lockfile, check the contents for a process-id to find  out  if  the
	      lockfile is still valid.

       -r retries
	      The  number of times dotlockfile retries to acquire the lock if it failed the first
	      time before giving up. The initial sleep after failing to acquire  the  lock  is	5
	      seconds.	After  each  next  try, a sleep of 5 seconds extra occurs up to a maximum
	      sleep of 60 seconds between tries.  The default number of retries is 5.

       -m     Lock or unlock the current users mailbox. The path to the mailbox  is  the  default
	      system  mailspool  directory  (usually  /var/mail) with the username as gotten from
	      getpwuid() appended. If the  environment	variable  $MAIL  is  set,  that  is  used
	      instead.	Then  the  string ".lock" is appended to get the name of the actual lock-
	      file.

       lockfile
	      The lockfile to be created/removed, unless the -m option is in effect.

RETURN VALUE
       Zero on success, and non-zero on failure. For the -c option, sucess  means  that  a  valid
       lockfile  is  already  present.	When  locking (the default, or the -l option) dotlockfile
       returns the same values as the library function lockfile_create(3). Unlocking a	non-exis-
       tant lockfile is not an error.

NOTES
       The  lockfile  is created exactly as named on the command line. The extension .lock is not
       automatically added.

       This utility is a lot like  the	lockfile(1)  utility  included	with  procmail,  and  the
       mutt_dotlock(1) utility included with mutt. However the command-line arguments differ, and
       so does the return status. It is believed that dotlockfile is the most flexible	implemen-
       tation,	since it automatically detects when it needs to use priviliges to lock a mailbox,
       and does it safely.

       The above mentioned lockfile_create(3) manpage is present in the liblockfile-dev package.

BUGS
       None known.

SEE ALSO
       lockfile_create(3), maillock(3)

AUTHOR
       Miquel van Smoorenburg, miquels@cistron.nl

					   15 May 2003				   DOTLOCKFILE(1)
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