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.\" ========================================================================
.\"
.IX Title "lib 3perl"
.TH lib 3perl 2024-05-30 "perl v5.38.2" "Perl Programmers Reference Guide"
.\" 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
lib \- manipulate @INC at compile time
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\&    use lib LIST;
\&
\&    no lib LIST;
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
This is a small simple module which simplifies the manipulation of \f(CW@INC\fR
at compile time.
.PP
It is typically used to add extra directories to perl's search path so
that later \f(CW\*(C`use\*(C'\fR or \f(CW\*(C`require\*(C'\fR statements will find modules which are
not located on perl's default search path.
.ie n .SS "Adding directories to @INC"
.el .SS "Adding directories to \f(CW@INC\fP"
.IX Subsection "Adding directories to @INC"
The parameters to \f(CW\*(C`use lib\*(C'\fR are added to the start of the perl search
path. Saying
.PP
.Vb 1
\&    use lib LIST;
.Ve
.PP
is \fIalmost\fR the same as saying
.PP
.Vb 1
\&    BEGIN { unshift(@INC, LIST) }
.Ve
.PP
For each directory in LIST (called \f(CW$dir\fR here) the lib module also
checks to see if a directory called \f(CW$dir\fR/$archname/auto exists.
If so the \f(CW$dir\fR/$archname directory is assumed to be a corresponding
architecture specific directory and is added to \f(CW@INC\fR in front of \f(CW$dir\fR.
lib.pm also checks if directories called \f(CW$dir\fR/$version and \f(CW$dir\fR/$version/$archname
exist and adds these directories to \f(CW@INC\fR.
.PP
The current value of \f(CW$archname\fR can be found with this command:
.PP
.Vb 1
\&    perl \-V:archname
.Ve
.PP
The corresponding command to get the current value of \f(CW$version\fR is:
.PP
.Vb 1
\&    perl \-V:version
.Ve
.PP
To avoid memory leaks, all trailing duplicate entries in \f(CW@INC\fR are
removed.
.ie n .SS "Deleting directories from @INC"
.el .SS "Deleting directories from \f(CW@INC\fP"
.IX Subsection "Deleting directories from @INC"
You should normally only add directories to \f(CW@INC\fR.  If you need to
delete directories from \f(CW@INC\fR take care to only delete those which you
added yourself or which you are certain are not needed by other modules
in your script.  Other modules may have added directories which they
need for correct operation.
.PP
The \f(CW\*(C`no lib\*(C'\fR statement deletes all instances of each named directory
from \f(CW@INC\fR.
.PP
For each directory in LIST (called \f(CW$dir\fR here) the lib module also
checks to see if a directory called \f(CW$dir\fR/$archname/auto exists.
If so the \f(CW$dir\fR/$archname directory is assumed to be a corresponding
architecture specific directory and is also deleted from \f(CW@INC\fR. lib.pm also
checks if directories called \f(CW$dir\fR/$version and \f(CW$dir\fR/$version/$archname
exist and deletes these directories from \f(CW@INC\fR.
.ie n .SS "Restoring original @INC"
.el .SS "Restoring original \f(CW@INC\fP"
.IX Subsection "Restoring original @INC"
When the lib module is first loaded it records the current value of \f(CW@INC\fR
in an array \f(CW@lib::ORIG_INC\fR. To restore \f(CW@INC\fR to that value you
can say
.PP
.Vb 1
\&    @INC = @lib::ORIG_INC;
.Ve
.SH CAVEATS
.IX Header "CAVEATS"
In order to keep lib.pm small and simple, it only works with Unix
filepaths.  This doesn't mean it only works on Unix, but non-Unix
users must first translate their file paths to Unix conventions.
.PP
.Vb 3
\&    # VMS users wanting to put [.stuff.moo] into 
\&    # their @INC would write
\&    use lib \*(Aqstuff/moo\*(Aq;
.Ve
.SH NOTES
.IX Header "NOTES"
In the future, this module will likely use File::Spec for determining
paths, as it does now for Mac OS (where Unix-style or Mac-style paths
work, and Unix-style paths are converted properly to Mac-style paths
before being added to \f(CW@INC\fR).
.PP
If you try to add a file to \f(CW@INC\fR as follows:
.PP
.Vb 1
\&  use lib \*(Aqthis_is_a_file.txt\*(Aq;
.Ve
.PP
\&\f(CW\*(C`lib\*(C'\fR will warn about this. The sole exceptions are files with the
\&\f(CW\*(C`.par\*(C'\fR extension which are intended to be used as libraries.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
FindBin \- optional module which deals with paths relative to the source file.
.PP
PAR \- optional module which can treat \f(CW\*(C`.par\*(C'\fR files as Perl libraries.
.SH AUTHOR
.IX Header "AUTHOR"
Tim Bunce, 2nd June 1995.
.PP
\&\f(CW\*(C`lib\*(C'\fR is maintained by the perl5\-porters. Please direct
any questions to the canonical mailing list. Anything that
is applicable to the CPAN release can be sent to its maintainer,
though.
.PP
Maintainer: The Perl5\-Porters <perl5\-porters@perl.org>
.PP
Maintainer of the CPAN release: Steffen Mueller <smueller@cpan.org>
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
This package has been part of the perl core since perl 5.001.
It has been released separately to CPAN so older installations
can benefit from bug fixes.
.PP
This package has the same copyright and license as the perl core.