DOTLOCKFILE(E)          Cistron Utilities          DOTLOCKFILE(E)



NAME
       dotlockfile - Utility to manage lockfiles

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

DESCRIPTION
       Dotlockfile is a command line utility  to  safely  create,
       test  and  remove  lockfiles.  Lockfiles are created in an
       NFS-safe way. Dotlockfile can 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.

       -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 tries to acquire
              the lock 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.

       -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 lockfile.

       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 pre-
       sent. When locking (the default, or the  -l  option)  dot-
       lockfile  returns  the same values as the library function
       lockfile_create(e).


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(e)  utility
       included with procmail, and  the  mutt_dotlock(k)  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 implementation, since it
       automatically detects when it needs to use  priviliges  to
       lock a mailbox, and does it safely.


BUGS
       None known.


SEE ALSO
       lockfile_create(e), maillock(k)


AUTHOR
       Miquel van Smoorenburg, miquels@cistron.nl



                           05 June 1999            DOTLOCKFILE(E)