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.\" ========================================================================
.\"
.IX Title "INN::Utils::Shlock 3pm"
.TH INN::Utils::Shlock 3pm "2023-04-16" "INN 2.7.2" "InterNetNews Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
INN::Utils::Shlock \- Wrapper around the shlock program
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This Perl module wraps the \fBshlock\fR\|(1) program so that it can easily be used.
Calling \fBshlock\fR is more portable than using \fBflock\fR\|(2) and its corresponding
Perl function because this function does not work as expected on all
existing systems.
.PP
See the \fBshlock\fR\|(1) documentation for more information.
.PP
Using INN::Utils::Shlock is straight-forward:
.PP
.Vb 2
\&    use lib \*(Aq<pathnews>/lib/perl\*(Aq;
\&    use INN::Utils::Shlock;
\&
\&    my $lockfile = "myprogram.LOCK";
\&
\&    # Acquire a lock.
\&    INN::Utils::Shlock::lock($lockfile);
\&
\&    # Do whatever you want.  The lock prevents concurrent accesses.
\&
\&    # Unlock.
\&    INN::Utils::Shlock::unlock($lockfile);
.Ve
.PP
These two functions return \f(CW1\fR on success, \f(CW0\fR on failure.  For example,
the success of (un)locking can be checked as:
.PP
.Vb 2
\&    INN::Utils::Shlock::lock($lockfile)
\&        or die "cannot create lock file";
.Ve
.PP
or:
.PP
.Vb 3
\&    if (! INN::Utils::Shlock::lock($lockfile, 4)) {
\&        die "giving up after 4 attempts to create lock file";
\&    }
.Ve
.PP
Instead of calling \f(CW\*(C`unlock(\f(CIlockfile\f(CW)\*(C'\fR, the \f(CW\*(C`releaselocks()\*(C'\fR
function can be called.  It removes any leftover locks, which is useful
when several different locks are used.  Another possible use is to call
it in an \s-1END\s0 code block:
.PP
.Vb 4
\&    END {
\&        # In case we bail out, while holding a lock.
\&        INN::Utils::Shlock::releaselocks();
\&    }
.Ve
.SH "INTERFACE"
.IX Header "INTERFACE"
.IP "lock(\fIlockfile\fR)" 4
.IX Item "lock(lockfile)"
Tries to create a lock file named \fIlockfile\fR.
.Sp
This function returns \f(CW1\fR on success, \f(CW0\fR on failure.
.IP "lock(\fIlockfile\fR, \fItries\fR)" 4
.IX Item "lock(lockfile, tries)"
Tries to create a lock file named \fIlockfile\fR.  If it fails, locking
attempts are repeated once every 2 seconds for at most \fItries\fR times
(including the first unsuccessful attempt).
.Sp
This function returns \f(CW1\fR on success, \f(CW0\fR on failure.
.IP "lock(\fIlockfile\fR, \fItries\fR, \fIdelay\fR)" 4
.IX Item "lock(lockfile, tries, delay)"
Tries to create a lock file named \fIlockfile\fR.  If it fails, locking
attempts are repeated once every \fIdelay\fR seconds for at most \fItries\fR
times (including the first unsuccessful attempt).
.Sp
Note that \f(CW\*(C`lock(\f(CIlockfile\f(CW)\*(C'\fR is equivalent to \f(CW\*(C`lock(\f(CIlockfile\f(CW,
1, 2)\*(C'\fR.
.Sp
This function returns \f(CW1\fR on success, \f(CW0\fR on failure.
.IP "\fBreleaselocks()\fR" 4
.IX Item "releaselocks()"
Removes all the lock files previously created by calling the \f(CW\*(C`lock(\f(CIlockfile\f(CW)\*(C'\fR function.
.Sp
This function returns the number of removed lock files.
.IP "unlock(\fIlockfile\fR)" 4
.IX Item "unlock(lockfile)"
Removes the file named \fIlockfile\fR.
.Sp
This function returns \f(CW1\fR on success, \f(CW0\fR on failure.
.SH "HISTORY"
.IX Header "HISTORY"
Documentation written by Julien Elie for InterNetNews.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBperl\fR\|(1), \fBshlock\fR\|(1).