Underline the fact that abs2rel() makes no sense

[p5sagit/p5-mst-13.2.git] / lib / File / Spec / Unix.pm

package File::Spec::Unix;

use strict;
use vars qw($VERSION);

$VERSION = '1.5';

=head1 NAME

File::Spec::Unix - File::Spec for Unix, base for other File::Spec modules

=head1 SYNOPSIS

 require File::Spec::Unix; # Done automatically by File::Spec

=head1 DESCRIPTION

Methods for manipulating file specifications.  Other File::Spec
modules, such as File::Spec::Mac, inherit from File::Spec::Unix and
override specific methods.

=head1 METHODS

=over 2

=item canonpath()

No physical check on the filesystem, but a logical cleanup of a
path. On UNIX eliminates successive slashes and successive "/.".

    $cpath = File::Spec->canonpath( $path ) ;

=cut

sub canonpath {
    my ($self,$path) = @_;
    
    # Handle POSIX-style node names beginning with double slash (qnx, nto)
    # Handle network path names beginning with double slash (cygwin)
    # (POSIX says: "a pathname that begins with two successive slashes
    # may be interpreted in an implementation-defined manner, although
    # more than two leading slashes shall be treated as a single slash.")
    my $node = '';
    if ( $^O =~ m/^(?:qnx|nto|cygwin)$/ && $path =~ s:^(//[^/]+)(/|\z):/:s ) {
      $node = $1;
    }
    # This used to be
    # $path =~ s|/+|/|g unless($^O eq 'cygwin');
    # but that made tests 29, 30, 35, 46, and 213 (as of #13272) to fail
    # (Mainly because trailing "" directories didn't get stripped).
    # Why would cygwin avoid collapsing multiple slashes into one? --jhi
    $path =~ s|/+|/|g;                             # xx////xx  -> xx/xx
    $path =~ s@(/\.)+(/|\Z(?!\n))@/@g;             # xx/././xx -> xx/xx
    $path =~ s|^(\./)+||s unless $path eq "./";    # ./xx      -> xx
    $path =~ s|^/(\.\./)+|/|s;                     # /../../xx -> xx
    $path =~ s|/\Z(?!\n)|| unless $path eq "/";          # xx/       -> xx
    return "$node$path";
}

=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
OS2. Of course, if this is the root directory, don't cut off the
trailing slash :-)

=cut

sub catdir {
    my $self = shift;
    my @args = @_;
    foreach (@args) {
	# append a slash to each argument unless it has one there
	$_ .= "/" if $_ eq '' || substr($_,-1) ne "/";
    }
    return $self->canonpath(join('', @args));
}

=item catfile

Concatenate one or more directory names and a filename to form a
complete path ending with a filename

=cut

sub catfile {
    my $self = shift;
    my $file = $self->canonpath(pop @_);
    return $file unless @_;
    my $dir = $self->catdir(@_);
    $dir .= "/" unless substr($dir,-1) eq "/";
    return $dir.$file;
}

=item curdir

Returns a string representation of the current directory.  "." on UNIX.

=cut

sub curdir {
    return ".";
}

=item devnull

Returns a string representation of the null device. "/dev/null" on UNIX.

=cut

sub devnull {
    return "/dev/null";
}

=item rootdir

Returns a string representation of the root directory.  "/" on UNIX.

=cut

sub rootdir {
    return "/";
}

=item tmpdir

Returns a string representation of the first writable directory from
the following list or the current directory if none from the list are
writable:

    $ENV{TMPDIR}
    /tmp

Since perl 5.8.0, if running under taint mode, and if $ENV{TMPDIR}
is tainted, it is not used.

=cut

my $tmpdir;
sub _tmpdir {
    return $tmpdir if defined $tmpdir;
    my $self = shift;
    my @dirlist = @_;
    {
	no strict 'refs';
	if (${"\cTAINT"}) { # Check for taint mode on perl >= 5.8.0
            require Scalar::Util;
	    @dirlist = grep { ! Scalar::Util::tainted($_) } @dirlist;
	}
    }
    foreach (@dirlist) {
	next unless defined && -d && -w _;
	$tmpdir = $_;
	last;
    }
    $tmpdir = $self->curdir unless defined $tmpdir;
    $tmpdir = defined $tmpdir && $self->canonpath($tmpdir);
    return $tmpdir;
}

sub tmpdir {
    return $tmpdir if defined $tmpdir;
    my $self = shift;
    $tmpdir = $self->_tmpdir( $ENV{TMPDIR}, "/tmp" );
}

=item updir

Returns a string representation of the parent directory.  ".." on UNIX.

=cut

sub updir {
    return "..";
}

=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.)

=cut

sub no_upwards {
    my $self = shift;
    return grep(!/^\.{1,2}\Z(?!\n)/s, @_);
}

=item case_tolerant

Returns a true or false value indicating, respectively, that alphabetic
is not or is significant when comparing file specifications.

=cut

sub case_tolerant {
    return 0;
}

=item file_name_is_absolute

Takes as argument a path and returns true if it is an absolute path.

This does not consult the local filesystem on Unix, Win32, OS/2 or Mac 
OS (Classic).  It does consult the working environment for VMS (see
L<File::Spec::VMS/file_name_is_absolute>).

=cut

sub file_name_is_absolute {
    my ($self,$file) = @_;
    return scalar($file =~ m:^/:s);
}

=item path

Takes no argument, returns the environment variable PATH as an array.

=cut

sub path {
    return () unless exists $ENV{PATH};
    my @path = split(':', $ENV{PATH});
    foreach (@path) { $_ = '.' if $_ eq '' }
    return @path;
}

=item join

join is the same as catfile.

=cut

sub join {
    my $self = shift;
    return $self->catfile(@_);
}

=item splitpath

    ($volume,$directories,$file) = File::Spec->splitpath( $path );
    ($volume,$directories,$file) = File::Spec->splitpath( $path, $no_file );

Splits a path into volume, directory, and filename portions. On systems
with no concept of volume, returns '' for volume. 

For systems with no syntax differentiating filenames from directories, 
assumes that the last file is a path unless $no_file is true or a 
trailing separator or /. or /.. is present. On Unix this means that $no_file
true makes this return ( '', $path, '' ).

The directory portion may or may not be returned with a trailing '/'.

The results can be passed to L</catpath()> to get back a path equivalent to
(usually identical to) the original path.

=cut

sub splitpath {
    my ($self,$path, $nofile) = @_;

    my ($volume,$directory,$file) = ('','','');

    if ( $nofile ) {
        $directory = $path;
    }
    else {
        $path =~ m|^ ( (?: .* / (?: \.\.?\Z(?!\n) )? )? ) ([^/]*) |xs;
        $directory = $1;
        $file      = $2;
    }

    return ($volume,$directory,$file);
}


=item splitdir

The opposite of L</catdir()>.

    @dirs = File::Spec->splitdir( $directories );

$directories 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.

Unlike just splitting the directories on the separator, empty
directory names (C<''>) can be returned, because these are significant
on some OSs.

On Unix,

    File::Spec->splitdir( "/a/b//c/" );

Yields:

    ( '', 'a', 'b', '', 'c', '' )

=cut

sub splitdir {
    return split m|/|, $_[1], -1;  # Preserve trailing fields
}


=item catpath()

Takes volume, directory and file portions and returns an entire path. Under
Unix, $volume is ignored, and directory and file are concatenated.  A '/' is
inserted if needed (though if the directory portion doesn't start with
'/' it is not added).  On other OSs, $volume is significant.

=cut

sub catpath {
    my ($self,$volume,$directory,$file) = @_;

    if ( $directory ne ''                && 
         $file ne ''                     && 
         substr( $directory, -1 ) ne '/' && 
         substr( $file, 0, 1 ) ne '/' 
    ) {
        $directory .= "/$file" ;
    }
    else {
        $directory .= $file ;
    }

    return $directory ;
}

=item abs2rel

Takes a destination path and an optional base path returns a relative path
from the base path to the destination path:

    $rel_path = File::Spec->abs2rel( $path ) ;
    $rel_path = File::Spec->abs2rel( $path, $base ) ;

If $base is not present or '', then L<cwd()|Cwd> is used. If $base is
relative, then it is converted to absolute form using
L</rel2abs()>. This means that it is taken to be relative to
L<cwd()|Cwd>.

On systems with the concept of a volume, this assumes that both paths
are on the $destination volume, and ignores the $base volume.  If this
assumption may be wrong (like in VMS), trying to "unify" the paths with
abs2rel() results in nonsense.

On systems that have a grammar that indicates filenames, this ignores the 
$base filename as well. Otherwise all path components are assumed to be
directories.

If $path is relative, it is converted to absolute form using L</rel2abs()>.
This means that it is taken to be relative to L<cwd()|Cwd>.

No checks against the filesystem are made.  On VMS, there is
interaction with the working environment, as logicals and
macros are expanded.

Based on code written by Shigio Yamaguchi.

=cut

sub abs2rel {
    my($self,$path,$base) = @_;

    # Clean up $path
    if ( ! $self->file_name_is_absolute( $path ) ) {
        $path = $self->rel2abs( $path ) ;
    }
    else {
        $path = $self->canonpath( $path ) ;
    }

    # Figure out the effective $base and clean it up.
    if ( !defined( $base ) || $base eq '' ) {
        $base = $self->_cwd();
    }
    elsif ( ! $self->file_name_is_absolute( $base ) ) {
        $base = $self->rel2abs( $base ) ;
    }
    else {
        $base = $self->canonpath( $base ) ;
    }

    # Now, remove all leading components that are the same
    my @pathchunks = $self->splitdir( $path);
    my @basechunks = $self->splitdir( $base);

    while (@pathchunks && @basechunks && $pathchunks[0] eq $basechunks[0]) {
        shift @pathchunks ;
        shift @basechunks ;
    }

    $path = CORE::join( '/', @pathchunks );
    $base = CORE::join( '/', @basechunks );

    # $base now contains the directories the resulting relative path 
    # must ascend out of before it can descend to $path_directory.  So, 
    # replace all names with $parentDir
    $base =~ s|[^/]+|..|g ;

    # Glue the two together, using a separator if necessary, and preventing an
    # empty result.
    if ( $path ne '' && $base ne '' ) {
        $path = "$base/$path" ;
    } else {
        $path = "$base$path" ;
    }

    return $self->canonpath( $path ) ;
}

=item rel2abs()

Converts a relative path to an absolute path. 

    $abs_path = File::Spec->rel2abs( $path ) ;
    $abs_path = File::Spec->rel2abs( $path, $base ) ;

If $base is not present or '', then L<cwd()|Cwd> is used. If $base is
relative, then it is converted to absolute form using
L</rel2abs()>. This means that it is taken to be relative to
L<cwd()|Cwd>.

On systems with the concept of a volume, this assumes that both paths 
are on the $base volume, and ignores the $path volume. 

On systems that have a grammar that indicates filenames, this ignores the 
$base filename as well. Otherwise all path components are assumed to be
directories.

If $path is absolute, it is cleaned up and returned using L</canonpath()>.

No checks against the filesystem are made.  On VMS, there is
interaction with the working environment, as logicals and
macros are expanded.

Based on code written by Shigio Yamaguchi.

=cut

sub rel2abs {
    my ($self,$path,$base ) = @_;

    # Clean up $path
    if ( ! $self->file_name_is_absolute( $path ) ) {
        # Figure out the effective $base and clean it up.
        if ( !defined( $base ) || $base eq '' ) {
	    $base = $self->_cwd();
        }
        elsif ( ! $self->file_name_is_absolute( $base ) ) {
            $base = $self->rel2abs( $base ) ;
        }
        else {
            $base = $self->canonpath( $base ) ;
        }

        # Glom them together
        $path = $self->catdir( $base, $path ) ;
    }

    return $self->canonpath( $path ) ;
}

=back

=head1 SEE ALSO

L<File::Spec>

=cut

# Internal routine to File::Spec, no point in making this public since
# it is the standard Cwd interface.  Most of the platform-specific
# File::Spec subclasses use this.
sub _cwd {
    require Cwd;
    Cwd::cwd();
}

1;