# dotlockfile(1) - man - phpman

[DOTLOCKFILE(1)](https://www.chedong.com/phpMan.php/man/DOTLOCKFILE/1/markdown)                            Cistron Utilities                           [DOTLOCKFILE(1)](https://www.chedong.com/phpMan.php/man/DOTLOCKFILE/1/markdown)



## NAME
       dotlockfile - Utility to manage lockfiles

## SYNOPSIS
       **dotlockfile** **-l** [**-r** _retries_] [**-i** _interval_] [**-p**] [**-q**] <**-m** | _lockfile_>
       **dotlockfile** **-l** [**-r** _retries_] [**-i** _interval_] [**-p**] [**-q**] <**-m** | _lockfile_> [**-P**] _cmd_ args ...
       **dotlockfile** -u **|** -t

## DESCRIPTION
       **dotlockfile** is a command line utility to reliably create, test and remove lockfiles.  It cre‐
       ates lockfiles _reliably_ on local and NFS filesystems, because the crucial  steps  of  testing
       for  a  preexisting  lockfile  and  creating  it are performed _atomically_ by a _single_ call to
       [_link_(2)](https://www.chedong.com/phpMan.php/man/link/2/markdown).  Manpage [_lockfile_create_(3)](https://www.chedong.com/phpMan.php/man/lockfilecreate/3/markdown) describes the used algorithm.

       **dotlockfile** is installed with attribute **SETGID** _mail_ and thus can also be used to lock and un‐
       lock 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
              cording to option **-r**.  Retry interval can be explicitly set with option **-i**.  This  op‐
              tion (**-l**) is the default, so it can be left off.

              A lockfile is treated as valid,
              •  if it holds the _process-id_ of a running process,
              •  or  if it does not hold any _process-id_ and has been touched less than 5 minutes ago
              (timestamp is younger than 5 minutes).

### -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 sec‐
              onds.  After each retry the sleep interval is increased incrementally by 5 seconds  up
              to  a  maximum sleep of 60 seconds between tries unless overridden by **-i**.  The default
              number of retries is 5.  To try only once, use "**-r** **0**".  To try indefinitely,  use  "**-r**
              **-1**".

### -i interval
              Sets a consistent retry interval.

### -u

### -t
              filesystems.  For lockfiles on local filesystems the **-p** option is preferable.

### -p
              ecuted) into the lockfile.  Also when testing for an existing lockfile, check the con‐
              tents for the _process-id_ of a running process to  verify  if  the  lockfile  is  still
              valid.  Obviously useful only for lockfiles on local filesystems.

### -m
              tem mailspool directory (usually _/var/mail_) with the username  as  gotten  from  _getp__‐
              _wuid_()  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.

### -q
              blockfile when it spawns **dotlockfile** as a helper program.

### -P
              the exit value of the spawned command.

       lockfile
              The lockfile to be created or removed.  Must not be specified  if  the  **-m**  option  is
              given.

       _command_ argument ...
              Create lockfile, run the _command_ , wait for it to exit, and remove lockfile.

## RETURN VALUE
       Zero  on success, and non-zero on failure.  When locking (the default, or with the **-l** option)
       **dotlockfile** returns the same values as the library function [_lockfile_create_(3)](https://www.chedong.com/phpMan.php/man/lockfilecreate/3/markdown).  Unlocking  a
       non-existent lockfile is not an error.

       Unless the **-P** option was supplied, when a command is executed, the return value does not cor‐
       respond with that of the command that was run.  If locking and unlocking was successful,  the
       exit status is zero.

## NOTES
       The  lockfile  is created exactly as named on the command line.  The extension "_.lock_" is _not_
       automatically appended.

       This utility is a lot like the [_lockfile_(1)](https://www.chedong.com/phpMan.php/man/lockfile/1/markdown) utility included with _procmail_, and the  _mutt_dot__‐
       [_lock_(1)](https://www.chedong.com/phpMan.php/man/lock/1/markdown)  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 privileges to lock a mailbox, and does it
       safely.

       The above mentioned [_lockfile_create_(3)](https://www.chedong.com/phpMan.php/man/lockfilecreate/3/markdown) manpage is present in the _liblockfile-dev_ package.

## BUGS
       None known.

## SEE ALSO
       [_lockfile_create_(3)](https://www.chedong.com/phpMan.php/man/lockfilecreate/3/markdown), [_maillock_(3)](https://www.chedong.com/phpMan.php/man/maillock/3/markdown)

## AUTHOR
       Miquel van Smoorenburg



                                          January 10, 2017                            [DOTLOCKFILE(1)](https://www.chedong.com/phpMan.php/man/DOTLOCKFILE/1/markdown)