file::spec.3

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.\" ========================================================================
.\"
.IX Title "File::Spec 3"
.TH File::Spec 3 "2008-01-23" "perl v5.10.0" "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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.SH "NAME"
File::Spec \- portably perform operations on file names
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&        use File::Spec;
\&
\&        $x=File::Spec\->catfile(\*(Aqa\*(Aq, \*(Aqb\*(Aq, \*(Aqc\*(Aq);
.Ve
.PP
which returns 'a/b/c' under Unix. Or:
.PP
.Vb 1
\&        use File::Spec::Functions;
\&
\&        $x = catfile(\*(Aqa\*(Aq, \*(Aqb\*(Aq, \*(Aqc\*(Aq);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This module is designed to support operations commonly performed on file
specifications (usually called \*(L"file names\*(R", but not to be confused with the
contents of a file, or Perl's file handles), such as concatenating several
directory and file names into a single path, or determining whether a path
is rooted. It is based on code directly taken from MakeMaker 5.17, code
written by Andreas Ko\*:nig, Andy Dougherty, Charles Bailey, Ilya
Zakharevich, Paul Schinder, and others.
.PP
Since these functions are different for most operating systems, each set of
\&\s-1OS\s0 specific routines is available in a separate module, including:
.PP
.Vb 5
\&        File::Spec::Unix
\&        File::Spec::Mac
\&        File::Spec::OS2
\&        File::Spec::Win32
\&        File::Spec::VMS
.Ve
.PP
The module appropriate for the current \s-1OS\s0 is automatically loaded by
File::Spec. Since some modules (like \s-1VMS\s0) make use of facilities available
only under that \s-1OS\s0, it may not be possible to load all modules under all
operating systems.
.PP
Since File::Spec is object oriented, subroutines should not be called directly,
as in:
.PP
.Vb 1
\&        File::Spec::catfile(\*(Aqa\*(Aq,\*(Aqb\*(Aq);
.Ve
.PP
but rather as class methods:
.PP
.Vb 1
\&        File::Spec\->catfile(\*(Aqa\*(Aq,\*(Aqb\*(Aq);
.Ve
.PP
For simple uses, File::Spec::Functions provides convenient functional
forms of these methods.
.SH "METHODS"
.IX Header "METHODS"
.IP "canonpath" 2
.IX Xref "canonpath"
.IX Item "canonpath"
No physical check on the filesystem, but a logical cleanup of a
path.
.Sp
.Vb 1
\&    $cpath = File::Spec\->canonpath( $path ) ;
.Ve
.Sp
Note that this does *not* collapse \fIx/../y\fR sections into \fIy\fR.  This
is by design.  If \fI/foo\fR on your system is a symlink to \fI/bar/baz\fR,
then \fI/foo/../quux\fR is actually \fI/bar/quux\fR, not \fI/quux\fR as a naive
\&\fI../\fR\-removal would give you.  If you want to do this kind of
processing, you probably want \f(CW\*(C`Cwd\*(C'\fR's \f(CW\*(C`realpath()\*(C'\fR function to
actually traverse the filesystem cleaning up paths like this.
.IP "catdir" 2
.IX Xref "catdir"
.IX Item "catdir"
Concatenate two or more directory names to form a complete path ending
with a directory. But remove the trailing slash from the resulting
string, because it doesn't look good, isn't necessary and confuses
\&\s-1OS/2\s0. Of course, if this is the root directory, don't cut off the
trailing slash :\-)
.Sp
.Vb 1
\&    $path = File::Spec\->catdir( @directories );
.Ve
.IP "catfile" 2
.IX Xref "catfile"
.IX Item "catfile"
Concatenate one or more directory names and a filename to form a
complete path ending with a filename
.Sp
.Vb 1
\&    $path = File::Spec\->catfile( @directories, $filename );
.Ve
.IP "curdir" 2
.IX Xref "curdir"
.IX Item "curdir"
Returns a string representation of the current directory.
.Sp
.Vb 1
\&    $curdir = File::Spec\->curdir();
.Ve
.IP "devnull" 2
.IX Xref "devnull"
.IX Item "devnull"
Returns a string representation of the null device.
.Sp
.Vb 1
\&    $devnull = File::Spec\->devnull();
.Ve
.IP "rootdir" 2
.IX Xref "rootdir"
.IX Item "rootdir"
Returns a string representation of the root directory.
.Sp
.Vb 1
\&    $rootdir = File::Spec\->rootdir();
.Ve
.IP "tmpdir" 2
.IX Xref "tmpdir"
.IX Item "tmpdir"
Returns a string representation of the first writable directory from a
list of possible temporary directories.  Returns the current directory
if no writable temporary directories are found.  The list of directories
checked depends on the platform; e.g. File::Spec::Unix checks \f(CW$ENV{TMPDIR}\fR
(unless taint is on) and \fI/tmp\fR.
.Sp
.Vb 1
\&    $tmpdir = File::Spec\->tmpdir();
.Ve
.IP "updir" 2
.IX Xref "updir"
.IX Item "updir"
Returns a string representation of the parent directory.
.Sp
.Vb 1
\&    $updir = File::Spec\->updir();
.Ve
.IP "no_upwards" 2
.IX Item "no_upwards"
Given a list of file names, strip out those that refer to a parent
directory. (Does not strip symlinks, only '.', '..', and equivalents.)
.Sp
.Vb 1
\&    @paths = File::Spec\->no_upwards( @paths );
.Ve
.IP "case_tolerant" 2
.IX Item "case_tolerant"
Returns a true or false value indicating, respectively, that alphabetic
case is not or is significant when comparing file specifications.
.Sp
.Vb 1
\&    $is_case_tolerant = File::Spec\->case_tolerant();
.Ve
.IP "file_name_is_absolute" 2
.IX Item "file_name_is_absolute"
Takes as its argument a path, and returns true if it is an absolute path.
.Sp
.Vb 1
\&    $is_absolute = File::Spec\->file_name_is_absolute( $path );
.Ve
.Sp
This does not consult the local filesystem on Unix, Win32, \s-1OS/2\s0, or
Mac \s-1OS\s0 (Classic).  It does consult the working environment for \s-1VMS\s0
(see \*(L"file_name_is_absolute\*(R" in File::Spec::VMS).
.IP "path" 2
.IX Xref "path"
.IX Item "path"
Takes no argument.  Returns the environment variable \f(CW\*(C`PATH\*(C'\fR (or the local
platform's equivalent) as a list.
.Sp
.Vb 1
\&    @PATH = File::Spec\->path();
.Ve
.IP "join" 2
.IX Xref "join, path"
.IX Item "join"
join is the same as catfile.
.IP "splitpath" 2
.IX Xref "splitpath split, path"
.IX Item "splitpath"
Splits a path in to volume, directory, and filename portions. On systems
with no concept of volume, returns '' for volume.
.Sp
.Vb 2
\&    ($volume,$directories,$file) = File::Spec\->splitpath( $path );
\&    ($volume,$directories,$file) = File::Spec\->splitpath( $path, $no_file );
.Ve
.Sp
For systems with no syntax differentiating filenames from directories, 
assumes that the last file is a path unless \f(CW$no_file\fR is true or a
trailing separator or \fI/.\fR or \fI/..\fR is present. On Unix, this means that \f(CW$no_file\fR
true makes this return ( '', \f(CW$path\fR, '' ).
.Sp
The directory portion may or may not be returned with a trailing '/'.
.Sp
The results can be passed to \*(L"\fIcatpath()\fR\*(R" to get back a path equivalent to
(usually identical to) the original path.
.IP "splitdir" 2
.IX Xref "splitdir split, dir"
.IX Item "splitdir"
The opposite of \*(L"\fIcatdir()\fR\*(R".
.Sp
.Vb 1
\&    @dirs = File::Spec\->splitdir( $directories );
.Ve
.Sp
\&\f(CW$directories\fR must be only the directory portion of the path on systems 
that have the concept of a volume or that have path syntax that differentiates
files from directories.
.Sp
Unlike just splitting the directories on the separator, empty
directory names (\f(CW\*(Aq\*(Aq\fR) can be returned, because these are significant
on some OSes.
.IP "\fIcatpath()\fR" 2
.IX Item "catpath()"
Takes volume, directory and file portions and returns an entire path. Under
Unix, \f(CW$volume\fR is ignored, and directory and file are concatenated.  A '/' is
inserted if need be.  On other OSes, \f(CW$volume\fR is significant.
.Sp
.Vb 1
\&    $full_path = File::Spec\->catpath( $volume, $directory, $file );
.Ve
.IP "abs2rel" 2
.IX Xref "abs2rel absolute, path relative, path"
.IX Item "abs2rel"
Takes a destination path and an optional base path returns a relative path
from the base path to the destination path:
.Sp
.Vb 2
\&    $rel_path = File::Spec\->abs2rel( $path ) ;
\&    $rel_path = File::Spec\->abs2rel( $path, $base ) ;
.Ve
.Sp
If \f(CW$base\fR is not present or '', then \fICwd::cwd()\fR is used. If \f(CW$base\fR is
relative, then it is converted to absolute form using
\&\*(L"\fIrel2abs()\fR\*(R". This means that it is taken to be relative to
\&\fICwd::cwd()\fR.
.Sp
On systems with the concept of volume, if \f(CW$path\fR and \f(CW$base\fR appear to be
on two different volumes, we will not attempt to resolve the two
paths, and we will instead simply return \f(CW$path\fR.  Note that previous
versions of this module ignored the volume of \f(CW$base\fR, which resulted in
garbage results part of the time.
.Sp
On systems that have a grammar that indicates filenames, this ignores the 
\&\f(CW$base\fR filename as well. Otherwise all path components are assumed to be
directories.
.Sp
If \f(CW$path\fR is relative, it is converted to absolute form using \*(L"\fIrel2abs()\fR\*(R".
This means that it is taken to be relative to \fICwd::cwd()\fR.
.Sp
No checks against the filesystem are made.  On \s-1VMS\s0, there is
interaction with the working environment, as logicals and
macros are expanded.
.Sp
Based on code written by Shigio Yamaguchi.
.IP "\fIrel2abs()\fR" 2
.IX Xref "rel2abs absolute, path relative, path"
.IX Item "rel2abs()"
Converts a relative path to an absolute path.
.Sp
.Vb 2
\&    $abs_path = File::Spec\->rel2abs( $path ) ;
\&    $abs_path = File::Spec\->rel2abs( $path, $base ) ;
.Ve
.Sp
If \f(CW$base\fR is not present or '', then \fICwd::cwd()\fR is used. If \f(CW$base\fR is relative,
then it is converted to absolute form using \*(L"\fIrel2abs()\fR\*(R". This means that it
is taken to be relative to \fICwd::cwd()\fR.
.Sp
On systems with the concept of volume, if \f(CW$path\fR and \f(CW$base\fR appear to be
on two different volumes, we will not attempt to resolve the two
paths, and we will instead simply return \f(CW$path\fR.  Note that previous
versions of this module ignored the volume of \f(CW$base\fR, which resulted in
garbage results part of the time.
.Sp
On systems that have a grammar that indicates filenames, this ignores the 
\&\f(CW$base\fR filename as well. Otherwise all path components are assumed to be
directories.
.Sp
If \f(CW$path\fR is absolute, it is cleaned up and returned using \*(L"\fIcanonpath()\fR\*(R".
.Sp
No checks against the filesystem are made.  On \s-1VMS\s0, there is
interaction with the working environment, as logicals and
macros are expanded.
.Sp
Based on code written by Shigio Yamaguchi.
.PP
For further information, please see File::Spec::Unix,
File::Spec::Mac, File::Spec::OS2, File::Spec::Win32, or
File::Spec::VMS.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
File::Spec::Unix, File::Spec::Mac, File::Spec::OS2,
File::Spec::Win32, File::Spec::VMS, File::Spec::Functions,
ExtUtils::MakeMaker
.SH "AUTHOR"
.IX Header "AUTHOR"
Currently maintained by Ken Williams \f(CW\*(C`<[e-mail]>\*(C'\fR.
.PP
The vast majority of the code was written by
Kenneth Albanowski \f(CW\*(C`<[e-mail]>\*(C'\fR,
Andy Dougherty \f(CW\*(C`<[e-mail]>\*(C'\fR,
Andreas Ko\*:nig \f(CW\*(C`<[e-mail]\-Berlin.DE>\*(C'\fR,
Tim Bunce \f(CW\*(C`<[e-mail]>\*(C'\fR.
\&\s-1VMS\s0 support by Charles Bailey \f(CW\*(C`<[e-mail]>\*(C'\fR.
\&\s-1OS/2\s0 support by Ilya Zakharevich \f(CW\*(C`<[e-mail]\-state.edu>\*(C'\fR.
Mac support by Paul Schinder \f(CW\*(C`<[e-mail]>\*(C'\fR, and
Thomas Wegner \f(CW\*(C`<[e-mail]>\*(C'\fR.
\&\fIabs2rel()\fR and \fIrel2abs()\fR written by Shigio Yamaguchi \f(CW\*(C`<[e-mail]>\*(C'\fR,
modified by Barrie Slaymaker \f(CW\*(C`<[e-mail]>\*(C'\fR.
\&\fIsplitpath()\fR, \fIsplitdir()\fR, \fIcatpath()\fR and \fIcatdir()\fR by Barrie Slaymaker.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright (c) 2004 by the Perl 5 Porters.  All rights reserved.
.PP
This program is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.