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.\" ========================================================================
.\"
.IX Title "Paranoid::Lockfile 3pm"
.TH Paranoid::Lockfile 3pm "2011-12-08" "perl v5.14.2" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
Paranoid::Lockfile \- Paranoid Lockfile support
.SH "VERSION"
.IX Header "VERSION"
\&\f(CW$Id:\fR Lockfile.pm,v 0.65 2011/12/08 07:53:07 acorliss Exp $
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&  use Paranoid::Lockfile;
\&
\&  $rv = plock($lockfile);
\&  $rv = punlock($lockfile);
\&  $rv = pcloseLockfile($lockfile);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This modules provides a relatively safe locking mechanism across multiple 
processes.  This does not work over \s-1NFS\s0 or across remote systems, this is 
only intended for use on a single system at a time, and only on those that 
support \fBflock\fR.
.PP
\&\fBsysopen\fR is used to avoid race conditions with multiple process attempting
to create the same file simultaneously.
.SH "SUBROUTINES/METHODS"
.IX Header "SUBROUTINES/METHODS"
.SS "plock"
.IX Subsection "plock"
.Vb 1
\&  $rv = plock($filename);
.Ve
.PP
This function attempts to safely create or open the lockfile.  It uses
\&\fBsysopen\fR with \fBO_CREAT | O_EXCL\fR to avoid race conditions with other
processes.  Returns a true if successful.
.PP
Your can pass an optional second argument which would be a string of either
\&'write' or 'shared'.  The default is 'write', which locks the file in
exclusive write mode.
.PP
You can pass an optional third argument which would be the lockfile
filesystem permissions if the file is created.  The default is 0600.
.PP
\&\fB\s-1NOTE:\s0\fR This function will block until the advisory lock is granted.
.SS "punlock"
.IX Subsection "punlock"
.Vb 1
\&  $rv = punlock($filename);
.Ve
.PP
This function removes any existing locks on the specified filename using
\&\fBflock\fR.  If no previous lock existed or it was successful it returns true.
This does not, however, close the open filehandle to the lockfile.
.SS "pcloseLockfile"
.IX Subsection "pcloseLockfile"
.Vb 1
\&  $rv = pcloseLockfile($filename);
.Ve
.PP
This function releases any existing locks and closes the open filehandle to
the lockfile.  Returns true if the file isn't currently open or the operation
succeeds.
.SH "DEPENDENCIES"
.IX Header "DEPENDENCIES"
.IP "o" 4
.IX Item "o"
Fcntl
.IP "o" 4
.IX Item "o"
Paranoid
.IP "o" 4
.IX Item "o"
Paranoid::Debug
.SH "BUGS AND LIMITATIONS"
.IX Header "BUGS AND LIMITATIONS"
.SH "AUTHOR"
.IX Header "AUTHOR"
Arthur Corliss (corliss@digitalmages.com)
.SH "LICENSE AND COPYRIGHT"
.IX Header "LICENSE AND COPYRIGHT"
This software is licensed under the same terms as Perl, itself. 
Please see http://dev.perl.org/licenses/ for more information.
.PP
(c) 2005, Arthur Corliss (corliss@digitalmages.com)