[p5sagit/p5-mst-13.2.git] / lib / Cwd.pm

package Cwd;
use 5.006;

=head1 NAME

Cwd - get pathname of current working directory

=head1 SYNOPSIS

    use Cwd;
    my $dir = getcwd;

    use Cwd 'abs_path';
    my $abs_path = abs_path($file);

=head1 DESCRIPTION

This module provides functions for determining the pathname of the
current working directory.  It is recommended that getcwd (or another
*cwd() function) be used in I<all> code to ensure portability.

By default, it exports the functions cwd(), getcwd(), fastcwd(), and
fastgetcwd() into the caller's namespace.  


=head2 getcwd and friends

Each of these functions are called without arguments and return the
absolute path of the current working directory.

=over 4

=item getcwd

    my $cwd = getcwd();

Returns the current working directory.

Re-implements the getcwd(3) (or getwd(3)) functions in Perl.

=item cwd

    my $cwd = cwd();

The cwd() is the most natural form for the current architecture. For
most systems it is identical to `pwd` (but without the trailing line
terminator).

Unfortunately, cwd() tends to break if called under taint mode.

=item fastcwd

    my $cwd = fastcwd();

A more dangerous version of getcwd(), but potentially faster.

It might conceivably chdir() you out of a directory that it can't
chdir() you back into.  If fastcwd encounters a problem it will return
undef but will probably leave you in a different directory.  For a
measure of extra security, if everything appears to have worked, the
fastcwd() function will check that it leaves you in the same directory
that it started in. If it has changed it will C<die> with the message
"Unstable directory path, current directory changed
unexpectedly". That should never happen.

=item fastgetcwd

  my $cwd = fastgetcwd();

The fastgetcwd() function is provided as a synonym for cwd().

=back


=head2 abs_path and friends

These functions are exported only on request.  They each take a single
argument and return the absolute pathname for it.

=over 4

=item abs_path

  my $abs_path = abs_path($file);

Uses the same algorithm as getcwd().  Symbolic links and relative-path
components ("." and "..") are resolved to return the canonical
pathname, just like realpath(3).

=item realpath

  my $abs_path = realpath($file);

A synonym for abs_path().

=item fast_abs_path

  my $abs_path = fast_abs_path($file);

A more dangerous, but potentially faster version of abs_path.

=back

=head2 $ENV{PWD}

If you ask to override your chdir() built-in function, 

  use Cwd qw(chdir);

then your PWD environment variable will be kept up to date.  Note that
it will only be kept up to date if all packages which use chdir import
it from Cwd.


=head1 NOTES

=over 4

=item *

Since the path seperators are different on some operating systems ('/'
on Unix, ':' on MacPerl, etc...) we recommend you use the File::Spec
modules wherever portability is a concern.

=item *

Actually, on Mac OS, the C<getcwd()>, C<fastgetcwd()> and C<fastcwd()>
functions  are all aliases for the C<cwd()> function, which, on Mac OS,
calls `pwd`. Likewise, the C<abs_path()> function is an alias for
C<fast_abs_path()>.

=back

=head1 SEE ALSO

L<File::chdir>

=cut

use strict;

use Carp;

our $VERSION = '2.06';

use base qw/ Exporter /;
our @EXPORT = qw(cwd getcwd fastcwd fastgetcwd);
our @EXPORT_OK = qw(chdir abs_path fast_abs_path realpath fast_realpath);

# sys_cwd may keep the builtin command

# All the functionality of this module may provided by builtins,
# there is no sense to process the rest of the file.
# The best choice may be to have this in BEGIN, but how to return from BEGIN?

if ($^O eq 'os2' && defined &sys_cwd && defined &sys_abspath) {
    local $^W = 0;
    *cwd		= \&sys_cwd;
    *getcwd		= \&cwd;
    *fastgetcwd		= \&cwd;
    *fastcwd		= \&cwd;
    *abs_path		= \&sys_abspath;
    *fast_abs_path	= \&abs_path;
    *realpath		= \&abs_path;
    *fast_realpath	= \&abs_path;
    return 1;
}

eval {
    require XSLoader;
    undef *Cwd::fastcwd; # avoid redefinition warning
    XSLoader::load('Cwd');
};


# Find the pwd command in the expected locations.  We assume these
# are safe.  This prevents _backtick_pwd() consulting $ENV{PATH}
# so everything works under taint mode.
my $pwd_cmd;
foreach my $try (qw(/bin/pwd /usr/bin/pwd)) {
    if( -x $try ) {
        $pwd_cmd = $try;
        last;
    }
}
$pwd_cmd ||= 'pwd';

# The 'natural and safe form' for UNIX (pwd may be setuid root)
sub _backtick_pwd {
    my $cwd = `$pwd_cmd`;
    # Belt-and-suspenders in case someone said "undef $/".
    local $/ = "\n";
    # `pwd` may fail e.g. if the disk is full
    chomp($cwd) if defined $cwd;
    $cwd;
}

# Since some ports may predefine cwd internally (e.g., NT)
# we take care not to override an existing definition for cwd().

unless(defined &cwd) {
    # The pwd command is not available in some chroot(2)'ed environments
    if( $^O eq 'MacOS' || (defined $ENV{PATH} && 
                           grep { -x "$_/pwd" } split(':', $ENV{PATH})) ) 
    {
	*cwd = \&_backtick_pwd;
    }
    else {
	*cwd = \&getcwd;
    }
}

# set a reasonable (and very safe) default for fastgetcwd, in case it
# isn't redefined later (20001212 rspier)
*fastgetcwd = \&cwd;

# By Brandon S. Allbery
#
# Usage: $cwd = getcwd();

sub getcwd
{
    abs_path('.');
}


# By John Bazik
#
# Usage: $cwd = &fastcwd;
#
# This is a faster version of getcwd.  It's also more dangerous because
# you might chdir out of a directory that you can't chdir back into.
    
sub fastcwd {
    my($odev, $oino, $cdev, $cino, $tdev, $tino);
    my(@path, $path);
    local(*DIR);

    my($orig_cdev, $orig_cino) = stat('.');
    ($cdev, $cino) = ($orig_cdev, $orig_cino);
    for (;;) {
	my $direntry;
	($odev, $oino) = ($cdev, $cino);
	CORE::chdir('..') || return undef;
	($cdev, $cino) = stat('.');
	last if $odev == $cdev && $oino == $cino;
	opendir(DIR, '.') || return undef;
	for (;;) {
	    $direntry = readdir(DIR);
	    last unless defined $direntry;
	    next if $direntry eq '.';
	    next if $direntry eq '..';

	    ($tdev, $tino) = lstat($direntry);
	    last unless $tdev != $odev || $tino != $oino;
	}
	closedir(DIR);
	return undef unless defined $direntry; # should never happen
	unshift(@path, $direntry);
    }
    $path = '/' . join('/', @path);
    if ($^O eq 'apollo') { $path = "/".$path; }
    # At this point $path may be tainted (if tainting) and chdir would fail.
    # To be more useful we untaint it then check that we landed where we started.
    $path = $1 if $path =~ /^(.*)\z/s;	# untaint
    CORE::chdir($path) || return undef;
    ($cdev, $cino) = stat('.');
    die "Unstable directory path, current directory changed unexpectedly"
	if $cdev != $orig_cdev || $cino != $orig_cino;
    $path;
}


# Keeps track of current working directory in PWD environment var
# Usage:
#	use Cwd 'chdir';
#	chdir $newdir;

my $chdir_init = 0;

sub chdir_init {
    if ($ENV{'PWD'} and $^O ne 'os2' and $^O ne 'dos' and $^O ne 'MSWin32') {
	my($dd,$di) = stat('.');
	my($pd,$pi) = stat($ENV{'PWD'});
	if (!defined $dd or !defined $pd or $di != $pi or $dd != $pd) {
	    $ENV{'PWD'} = cwd();
	}
    }
    else {
	my $wd = cwd();
	$wd = Win32::GetFullPathName($wd) if $^O eq 'MSWin32';
	$ENV{'PWD'} = $wd;
    }
    # Strip an automounter prefix (where /tmp_mnt/foo/bar == /foo/bar)
    if ($^O ne 'MSWin32' and $ENV{'PWD'} =~ m|(/[^/]+(/[^/]+/[^/]+))(.*)|s) {
	my($pd,$pi) = stat($2);
	my($dd,$di) = stat($1);
	if (defined $pd and defined $dd and $di == $pi and $dd == $pd) {
	    $ENV{'PWD'}="$2$3";
	}
    }
    $chdir_init = 1;
}

sub chdir {
    my $newdir = @_ ? shift : '';	# allow for no arg (chdir to HOME dir)
    $newdir =~ s|///*|/|g unless $^O eq 'MSWin32';
    chdir_init() unless $chdir_init;
    my $newpwd;
    if ($^O eq 'MSWin32') {
	# get the full path name *before* the chdir()
	$newpwd = Win32::GetFullPathName($newdir);
    }

    return 0 unless CORE::chdir $newdir;

    if ($^O eq 'VMS') {
	return $ENV{'PWD'} = $ENV{'DEFAULT'}
    }
    elsif ($^O eq 'MacOS') {
	return $ENV{'PWD'} = cwd();
    }
    elsif ($^O eq 'MSWin32') {
	$ENV{'PWD'} = $newpwd;
	return 1;
    }

    if ($newdir =~ m#^/#s) {
	$ENV{'PWD'} = $newdir;
    } else {
	my @curdir = split(m#/#,$ENV{'PWD'});
	@curdir = ('') unless @curdir;
	my $component;
	foreach $component (split(m#/#, $newdir)) {
	    next if $component eq '.';
	    pop(@curdir),next if $component eq '..';
	    push(@curdir,$component);
	}
	$ENV{'PWD'} = join('/',@curdir) || '/';
    }
    1;
}


# In case the XS version doesn't load.
*abs_path = \&_perl_abs_path unless defined &abs_path;
sub _perl_abs_path
{
    my $start = @_ ? shift : '.';
    my($dotdots, $cwd, @pst, @cst, $dir, @tst);

    unless (@cst = stat( $start ))
    {
	carp "stat($start): $!";
	return '';
    }
    $cwd = '';
    $dotdots = $start;
    do
    {
	$dotdots .= '/..';
	@pst = @cst;
	unless (opendir(PARENT, $dotdots))
	{
	    carp "opendir($dotdots): $!";
	    return '';
	}
	unless (@cst = stat($dotdots))
	{
	    carp "stat($dotdots): $!";
	    closedir(PARENT);
	    return '';
	}
	if ($pst[0] == $cst[0] && $pst[1] == $cst[1])
	{
	    $dir = undef;
	}
	else
	{
	    do
	    {
		unless (defined ($dir = readdir(PARENT)))
	        {
		    carp "readdir($dotdots): $!";
		    closedir(PARENT);
		    return '';
		}
		$tst[0] = $pst[0]+1 unless (@tst = lstat("$dotdots/$dir"))
	    }
	    while ($dir eq '.' || $dir eq '..' || $tst[0] != $pst[0] ||
		   $tst[1] != $pst[1]);
	}
	$cwd = (defined $dir ? "$dir" : "" ) . "/$cwd" ;
	closedir(PARENT);
    } while (defined $dir);
    chop($cwd) unless $cwd eq '/'; # drop the trailing /
    $cwd;
}


# added function alias for those of us more
# used to the libc function.  --tchrist 27-Jan-00
*realpath = \&abs_path;

sub fast_abs_path {
    my $cwd = getcwd();
    require File::Spec;
    my $path = @_ ? shift : File::Spec->curdir;
    CORE::chdir($path) || croak "Cannot chdir to $path:$!";
    my $realpath = getcwd();
    CORE::chdir($cwd)  || croak "Cannot chdir back to $cwd:$!";
    $realpath;
}

# added function alias to follow principle of least surprise
# based on previous aliasing.  --tchrist 27-Jan-00
*fast_realpath = \&fast_abs_path;


# --- PORTING SECTION ---

# VMS: $ENV{'DEFAULT'} points to default directory at all times
# 06-Mar-1996  Charles Bailey  bailey@newman.upenn.edu
# Note: Use of Cwd::chdir() causes the logical name PWD to be defined
#   in the process logical name table as the default device and directory
#   seen by Perl. This may not be the same as the default device
#   and directory seen by DCL after Perl exits, since the effects
#   the CRTL chdir() function persist only until Perl exits.

sub _vms_cwd {
    return $ENV{'DEFAULT'};
}

sub _vms_abs_path {
    return $ENV{'DEFAULT'} unless @_;
    my $path = VMS::Filespec::pathify($_[0]);
    croak("Invalid path name $_[0]") unless defined $path;
    return VMS::Filespec::rmsexpand($path);
}

sub _os2_cwd {
    $ENV{'PWD'} = `cmd /c cd`;
    chop $ENV{'PWD'};
    $ENV{'PWD'} =~ s:\\:/:g ;
    return $ENV{'PWD'};
}

sub _win32_cwd {
    $ENV{'PWD'} = Win32::GetCwd();
    $ENV{'PWD'} =~ s:\\:/:g ;
    return $ENV{'PWD'};
}

*_NT_cwd = \&_win32_cwd if (!defined &_NT_cwd && 
                            defined &Win32::GetCwd);

*_NT_cwd = \&_os2_cwd unless defined &_NT_cwd;

sub _dos_cwd {
    if (!defined &Dos::GetCwd) {
        $ENV{'PWD'} = `command /c cd`;
        chop $ENV{'PWD'};
        $ENV{'PWD'} =~ s:\\:/:g ;
    } else {
        $ENV{'PWD'} = Dos::GetCwd();
    }
    return $ENV{'PWD'};
}

sub _qnx_cwd {
	local $ENV{PATH} = '';
	local $ENV{CDPATH} = '';
	local $ENV{ENV} = '';
    $ENV{'PWD'} = `/usr/bin/fullpath -t`;
    chop $ENV{'PWD'};
    return $ENV{'PWD'};
}

sub _qnx_abs_path {
	local $ENV{PATH} = '';
	local $ENV{CDPATH} = '';
	local $ENV{ENV} = '';
    my $path = @_ ? shift : '.';
    my $realpath=`/usr/bin/fullpath -t $path`;
    chop $realpath;
    return $realpath;
}

sub _epoc_cwd {
    $ENV{'PWD'} = EPOC::getcwd();
    return $ENV{'PWD'};
}

{
    no warnings;	# assignments trigger 'subroutine redefined' warning

    if ($^O eq 'VMS') {
        *cwd		= \&_vms_cwd;
        *getcwd		= \&_vms_cwd;
        *fastcwd	= \&_vms_cwd;
        *fastgetcwd	= \&_vms_cwd;
        *abs_path	= \&_vms_abs_path;
        *fast_abs_path	= \&_vms_abs_path;
    }
    elsif ($^O eq 'NT' or $^O eq 'MSWin32') {
        # We assume that &_NT_cwd is defined as an XSUB or in the core.
        *cwd		= \&_NT_cwd;
        *getcwd		= \&_NT_cwd;
        *fastcwd	= \&_NT_cwd;
        *fastgetcwd	= \&_NT_cwd;
        *abs_path	= \&fast_abs_path;
        *realpath   = \&fast_abs_path;
    }
    elsif ($^O eq 'os2') {
        # sys_cwd may keep the builtin command
        *cwd		= defined &sys_cwd ? \&sys_cwd : \&_os2_cwd;
        *getcwd		= \&cwd;
        *fastgetcwd	= \&cwd;
        *fastcwd	= \&cwd;
        *abs_path	= \&fast_abs_path;
    }
    elsif ($^O eq 'dos') {
        *cwd		= \&_dos_cwd;
        *getcwd		= \&_dos_cwd;
        *fastgetcwd	= \&_dos_cwd;
        *fastcwd	= \&_dos_cwd;
        *abs_path	= \&fast_abs_path;
    }
    elsif ($^O =~ m/^(?:qnx|nto)$/ ) {
        *cwd		= \&_qnx_cwd;
        *getcwd		= \&_qnx_cwd;
        *fastgetcwd	= \&_qnx_cwd;
        *fastcwd	= \&_qnx_cwd;
        *abs_path	= \&_qnx_abs_path;
        *fast_abs_path	= \&_qnx_abs_path;
    }
    elsif ($^O eq 'cygwin') {
        *getcwd	= \&cwd;
        *fastgetcwd	= \&cwd;
        *fastcwd	= \&cwd;
        *abs_path	= \&fast_abs_path;
    }
    elsif ($^O eq 'epoc') {
        *cwd            = \&_epoc_cwd;
        *getcwd	        = \&_epoc_cwd;
        *fastgetcwd	= \&_epoc_cwd;
        *fastcwd	= \&_epoc_cwd;
        *abs_path	= \&fast_abs_path;
    }
    elsif ($^O eq 'MacOS') {
    	*getcwd     = \&cwd;
    	*fastgetcwd = \&cwd;
    	*fastcwd    = \&cwd;
    	*abs_path   = \&fast_abs_path;
    }
}


1;
Commit	Line	Data
a0d0e21e	1	package Cwd;
3b825e41	2	use 5.006;
a0d0e21e	3
f06db76b	4	=head1 NAME
f06db76b	5
902bacac	6	Cwd - get pathname of current working directory
f06db76b	7
	8	=head1 SYNOPSIS
	9
4633a7c4	10	use Cwd;
04929354	11	my $dir = getcwd;
4633a7c4	12
04929354	13	use Cwd 'abs_path';
04929354	14	my $abs_path = abs_path($file);
f06db76b	15
04929354	16	=head1 DESCRIPTION
902bacac	17
04929354	18	This module provides functions for determining the pathname of the
	19	current working directory. It is recommended that getcwd (or another
	20	*cwd() function) be used in I<all> code to ensure portability.
f06db76b	21
04929354	22	By default, it exports the functions cwd(), getcwd(), fastcwd(), and
04929354	23	fastgetcwd() into the caller's namespace.
f06db76b	24
20408e3c	25
04929354	26	=head2 getcwd and friends
20408e3c	27
04929354	28	Each of these functions are called without arguments and return the
04929354	29	absolute path of the current working directory.
f06db76b	30
04929354	31	=over 4
	32
	33	=item getcwd
	34
	35	my $cwd = getcwd();
	36
	37	Returns the current working directory.
	38
	39	Re-implements the getcwd(3) (or getwd(3)) functions in Perl.
	40
	41	=item cwd
	42
	43	my $cwd = cwd();
	44
	45	The cwd() is the most natural form for the current architecture. For
	46	most systems it is identical to `pwd` (but without the trailing line
	47	terminator).
	48
	49	Unfortunately, cwd() tends to break if called under taint mode.
	50
	51	=item fastcwd
	52
	53	my $cwd = fastcwd();
	54
	55	A more dangerous version of getcwd(), but potentially faster.
	56
	57	It might conceivably chdir() you out of a directory that it can't
	58	chdir() you back into. If fastcwd encounters a problem it will return
	59	undef but will probably leave you in a different directory. For a
	60	measure of extra security, if everything appears to have worked, the
	61	fastcwd() function will check that it leaves you in the same directory
	62	that it started in. If it has changed it will C<die> with the message
	63	"Unstable directory path, current directory changed
	64	unexpectedly". That should never happen.
	65
	66	=item fastgetcwd
	67
	68	my $cwd = fastgetcwd();
f06db76b	69
902bacac	70	The fastgetcwd() function is provided as a synonym for cwd().
fb73857a	71
04929354	72	=back
04929354	73
902bacac	74
04929354	75	=head2 abs_path and friends
	76
	77	These functions are exported only on request. They each take a single
	78	argument and return the absolute pathname for it.
	79
	80	=over 4
	81
	82	=item abs_path
	83
	84	my $abs_path = abs_path($file);
	85
	86	Uses the same algorithm as getcwd(). Symbolic links and relative-path
	87	components ("." and "..") are resolved to return the canonical
	88	pathname, just like realpath(3).
	89
	90	=item realpath
	91
	92	my $abs_path = realpath($file);
	93
	94	A synonym for abs_path().
	95
	96	=item fast_abs_path
	97
510179aa	98	my $abs_path = fast_abs_path($file);
04929354	99
	100	A more dangerous, but potentially faster version of abs_path.
	101
	102	=back
	103
	104	=head2 $ENV{PWD}
	105
	106	If you ask to override your chdir() built-in function,
	107
	108	use Cwd qw(chdir);
	109
	110	then your PWD environment variable will be kept up to date. Note that
	111	it will only be kept up to date if all packages which use chdir import
	112	it from Cwd.
4633a7c4	113
4633a7c4	114
4d6b4052	115	=head1 NOTES
	116
	117	=over 4
	118
	119	=item *
	120
04929354	121	Since the path seperators are different on some operating systems ('/'
	122	on Unix, ':' on MacPerl, etc...) we recommend you use the File::Spec
	123	modules wherever portability is a concern.
	124
04929354	125	=item *
4d6b4052	126
	127	Actually, on Mac OS, the C<getcwd()>, C<fastgetcwd()> and C<fastcwd()>
	128	functions are all aliases for the C<cwd()> function, which, on Mac OS,
	129	calls `pwd`. Likewise, the C<abs_path()> function is an alias for
	130	C<fast_abs_path()>.
	131
	132	=back
	133
04929354	134	=head1 SEE ALSO
	135
	136	L<File::chdir>
	137
f06db76b	138	=cut
f06db76b	139
b060a406	140	use strict;
96e4d5b1	141
	142	use Carp;
	143
04929354	144	our $VERSION = '2.06';
96e4d5b1	145
b060a406	146	use base qw/ Exporter /;
	147	our @EXPORT = qw(cwd getcwd fastcwd fastgetcwd);
	148	our @EXPORT_OK = qw(chdir abs_path fast_abs_path realpath fast_realpath);
a0d0e21e	149
f5f423e4	150	# sys_cwd may keep the builtin command
	151
	152	# All the functionality of this module may provided by builtins,
	153	# there is no sense to process the rest of the file.
	154	# The best choice may be to have this in BEGIN, but how to return from BEGIN?
	155
	156	if ($^O eq 'os2' && defined &sys_cwd && defined &sys_abspath) {
	157	local $^W = 0;
	158	*cwd = \&sys_cwd;
	159	*getcwd = \&cwd;
	160	*fastgetcwd = \&cwd;
	161	*fastcwd = \&cwd;
	162	*abs_path = \&sys_abspath;
	163	*fast_abs_path = \&abs_path;
	164	*realpath = \&abs_path;
	165	*fast_realpath = \&abs_path;
	166	return 1;
	167	}
	168
f22d8e4b	169	eval {
f22d8e4b	170	require XSLoader;
716e3b8c	171	undef *Cwd::fastcwd; # avoid redefinition warning
f22d8e4b	172	XSLoader::load('Cwd');
f22d8e4b	173	};
4633a7c4	174
96e4d5b1	175
3547aa9a	176	# Find the pwd command in the expected locations. We assume these
	177	# are safe. This prevents _backtick_pwd() consulting $ENV{PATH}
	178	# so everything works under taint mode.
	179	my $pwd_cmd;
	180	foreach my $try (qw(/bin/pwd /usr/bin/pwd)) {
	181	if( -x $try ) {
	182	$pwd_cmd = $try;
	183	last;
	184	}
	185	}
	186	$pwd_cmd \|\|= 'pwd';
	187
	188	# The 'natural and safe form' for UNIX (pwd may be setuid root)
8b88ae92	189	sub _backtick_pwd {
3547aa9a	190	my $cwd = `$pwd_cmd`;
ac3b20cb	191	# Belt-and-suspenders in case someone said "undef $/".
5cf6da5f	192	local $/ = "\n";
ac3b20cb	193	# `pwd` may fail e.g. if the disk is full
7e03f963	194	chomp($cwd) if defined $cwd;
4633a7c4	195	$cwd;
8b88ae92	196	}
4633a7c4	197
	198	# Since some ports may predefine cwd internally (e.g., NT)
	199	# we take care not to override an existing definition for cwd().
	200
ea54c8bd	201	unless(defined &cwd) {
ea54c8bd	202	# The pwd command is not available in some chroot(2)'ed environments
73b801a6	203	if( $^O eq 'MacOS' \|\| (defined $ENV{PATH} &&
	204	grep { -x "$_/pwd" } split(':', $ENV{PATH})) )
	205	{
ea54c8bd	206	*cwd = \&_backtick_pwd;
	207	}
	208	else {
	209	*cwd = \&getcwd;
	210	}
	211	}
a0d0e21e	212
1f4f94f5	213	# set a reasonable (and very safe) default for fastgetcwd, in case it
	214	# isn't redefined later (20001212 rspier)
	215	*fastgetcwd = \&cwd;
748a9306	216
a0d0e21e	217	# By Brandon S. Allbery
	218	#
	219	# Usage: $cwd = getcwd();
	220
	221	sub getcwd
	222	{
07569ed3	223	abs_path('.');
a0d0e21e	224	}
a0d0e21e	225
a0c9c202	226
	227	# By John Bazik
	228	#
	229	# Usage: $cwd = &fastcwd;
	230	#
	231	# This is a faster version of getcwd. It's also more dangerous because
	232	# you might chdir out of a directory that you can't chdir back into.
	233
	234	sub fastcwd {
	235	my($odev, $oino, $cdev, $cino, $tdev, $tino);
	236	my(@path, $path);
	237	local(*DIR);
	238
	239	my($orig_cdev, $orig_cino) = stat('.');
	240	($cdev, $cino) = ($orig_cdev, $orig_cino);
	241	for (;;) {
	242	my $direntry;
	243	($odev, $oino) = ($cdev, $cino);
	244	CORE::chdir('..') \|\| return undef;
	245	($cdev, $cino) = stat('.');
	246	last if $odev == $cdev && $oino == $cino;
	247	opendir(DIR, '.') \|\| return undef;
	248	for (;;) {
	249	$direntry = readdir(DIR);
	250	last unless defined $direntry;
	251	next if $direntry eq '.';
	252	next if $direntry eq '..';
	253
	254	($tdev, $tino) = lstat($direntry);
	255	last unless $tdev != $odev \|\| $tino != $oino;
	256	}
	257	closedir(DIR);
	258	return undef unless defined $direntry; # should never happen
	259	unshift(@path, $direntry);
	260	}
	261	$path = '/' . join('/', @path);
	262	if ($^O eq 'apollo') { $path = "/".$path; }
	263	# At this point $path may be tainted (if tainting) and chdir would fail.
	264	# To be more useful we untaint it then check that we landed where we started.
	265	$path = $1 if $path =~ /^(.*)\z/s; # untaint
	266	CORE::chdir($path) \|\| return undef;
	267	($cdev, $cino) = stat('.');
	268	die "Unstable directory path, current directory changed unexpectedly"
	269	if $cdev != $orig_cdev \|\| $cino != $orig_cino;
	270	$path;
	271	}
	272
	273
4633a7c4	274	# Keeps track of current working directory in PWD environment var
a0d0e21e	275	# Usage:
	276	# use Cwd 'chdir';
	277	# chdir $newdir;
	278
4633a7c4	279	my $chdir_init = 0;
a0d0e21e	280
4633a7c4	281	sub chdir_init {
3b8e3443	282	if ($ENV{'PWD'} and $^O ne 'os2' and $^O ne 'dos' and $^O ne 'MSWin32') {
a0d0e21e	283	my($dd,$di) = stat('.');
	284	my($pd,$pi) = stat($ENV{'PWD'});
	285	if (!defined $dd or !defined $pd or $di != $pi or $dd != $pd) {
4633a7c4	286	$ENV{'PWD'} = cwd();
a0d0e21e	287	}
	288	}
	289	else {
3b8e3443	290	my $wd = cwd();
	291	$wd = Win32::GetFullPathName($wd) if $^O eq 'MSWin32';
	292	$ENV{'PWD'} = $wd;
a0d0e21e	293	}
4633a7c4	294	# Strip an automounter prefix (where /tmp_mnt/foo/bar == /foo/bar)
3b8e3443	295	if ($^O ne 'MSWin32' and $ENV{'PWD'} =~ m\|(/[^/]+(/[^/]+/[^/]+))(.*)\|s) {
a0d0e21e	296	my($pd,$pi) = stat($2);
	297	my($dd,$di) = stat($1);
	298	if (defined $pd and defined $dd and $di == $pi and $dd == $pd) {
	299	$ENV{'PWD'}="$2$3";
	300	}
	301	}
	302	$chdir_init = 1;
	303	}
	304
	305	sub chdir {
22978713	306	my $newdir = @_ ? shift : ''; # allow for no arg (chdir to HOME dir)
3b8e3443	307	$newdir =~ s\|///*\|/\|g unless $^O eq 'MSWin32';
a0d0e21e	308	chdir_init() unless $chdir_init;
4ffa1610	309	my $newpwd;
	310	if ($^O eq 'MSWin32') {
	311	# get the full path name before the chdir()
	312	$newpwd = Win32::GetFullPathName($newdir);
	313	}
	314
4633a7c4	315	return 0 unless CORE::chdir $newdir;
4ffa1610	316
3b8e3443	317	if ($^O eq 'VMS') {
	318	return $ENV{'PWD'} = $ENV{'DEFAULT'}
	319	}
4aecb5b5	320	elsif ($^O eq 'MacOS') {
	321	return $ENV{'PWD'} = cwd();
	322	}
3b8e3443	323	elsif ($^O eq 'MSWin32') {
4ffa1610	324	$ENV{'PWD'} = $newpwd;
3b8e3443	325	return 1;
3b8e3443	326	}
748a9306	327
392d8ab8	328	if ($newdir =~ m#^/#s) {
a0d0e21e	329	$ENV{'PWD'} = $newdir;
4633a7c4	330	} else {
	331	my @curdir = split(m#/#,$ENV{'PWD'});
	332	@curdir = ('') unless @curdir;
	333	my $component;
a0d0e21e	334	foreach $component (split(m#/#, $newdir)) {
	335	next if $component eq '.';
	336	pop(@curdir),next if $component eq '..';
	337	push(@curdir,$component);
	338	}
	339	$ENV{'PWD'} = join('/',@curdir) \|\| '/';
	340	}
4633a7c4	341	1;
a0d0e21e	342	}
a0d0e21e	343
a0c9c202	344
	345	# In case the XS version doesn't load.
	346	*abs_path = \&_perl_abs_path unless defined &abs_path;
	347	sub _perl_abs_path
	348	{
	349	my $start = @_ ? shift : '.';
	350	my($dotdots, $cwd, @pst, @cst, $dir, @tst);
	351
	352	unless (@cst = stat( $start ))
	353	{
	354	carp "stat($start): $!";
	355	return '';
	356	}
	357	$cwd = '';
	358	$dotdots = $start;
	359	do
	360	{
	361	$dotdots .= '/..';
	362	@pst = @cst;
	363	unless (opendir(PARENT, $dotdots))
	364	{
	365	carp "opendir($dotdots): $!";
	366	return '';
	367	}
	368	unless (@cst = stat($dotdots))
	369	{
	370	carp "stat($dotdots): $!";
	371	closedir(PARENT);
	372	return '';
	373	}
	374	if ($pst[0] == $cst[0] && $pst[1] == $cst[1])
	375	{
	376	$dir = undef;
	377	}
	378	else
	379	{
	380	do
	381	{
	382	unless (defined ($dir = readdir(PARENT)))
	383	{
	384	carp "readdir($dotdots): $!";
	385	closedir(PARENT);
	386	return '';
	387	}
	388	$tst[0] = $pst[0]+1 unless (@tst = lstat("$dotdots/$dir"))
	389	}
	390	while ($dir eq '.' \|\| $dir eq '..' \|\| $tst[0] != $pst[0] \|\|
	391	$tst[1] != $pst[1]);
	392	}
	393	$cwd = (defined $dir ? "$dir" : "" ) . "/$cwd" ;
	394	closedir(PARENT);
	395	} while (defined $dir);
	396	chop($cwd) unless $cwd eq '/'; # drop the trailing /
	397	$cwd;
	398	}
	399
	400
e4c51978	401	# added function alias for those of us more
	402	# used to the libc function. --tchrist 27-Jan-00
	403	*realpath = \&abs_path;
	404
96e4d5b1	405	sub fast_abs_path {
96e4d5b1	406	my $cwd = getcwd();
4d6b4052	407	require File::Spec;
4d6b4052	408	my $path = @_ ? shift : File::Spec->curdir;
e79e61e4	409	CORE::chdir($path) \|\| croak "Cannot chdir to $path:$!";
96e4d5b1	410	my $realpath = getcwd();
e79e61e4	411	CORE::chdir($cwd) \|\| croak "Cannot chdir back to $cwd:$!";
96e4d5b1	412	$realpath;
8b88ae92	413	}
8b88ae92	414
e4c51978	415	# added function alias to follow principle of least surprise
	416	# based on previous aliasing. --tchrist 27-Jan-00
	417	*fast_realpath = \&fast_abs_path;
	418
4633a7c4	419
	420	# --- PORTING SECTION ---
	421
	422	# VMS: $ENV{'DEFAULT'} points to default directory at all times
bd3fa61c	423	# 06-Mar-1996 Charles Bailey bailey@newman.upenn.edu
c6538b72	424	# Note: Use of Cwd::chdir() causes the logical name PWD to be defined
8b88ae92	425	# in the process logical name table as the default device and directory
8b88ae92	426	# seen by Perl. This may not be the same as the default device
4633a7c4	427	# and directory seen by DCL after Perl exits, since the effects
4633a7c4	428	# the CRTL chdir() function persist only until Perl exits.
4633a7c4	429
4633a7c4	430	sub _vms_cwd {
96e4d5b1	431	return $ENV{'DEFAULT'};
	432	}
	433
	434	sub _vms_abs_path {
	435	return $ENV{'DEFAULT'} unless @_;
	436	my $path = VMS::Filespec::pathify($_[0]);
	437	croak("Invalid path name $_[0]") unless defined $path;
	438	return VMS::Filespec::rmsexpand($path);
4633a7c4	439	}
68dc0745	440
4633a7c4	441	sub _os2_cwd {
	442	$ENV{'PWD'} = `cmd /c cd`;
	443	chop $ENV{'PWD'};
aa6b7957	444	$ENV{'PWD'} =~ s:\\:/:g ;
4633a7c4	445	return $ENV{'PWD'};
	446	}
	447
96e4d5b1	448	sub _win32_cwd {
2d7a9237	449	$ENV{'PWD'} = Win32::GetCwd();
aa6b7957	450	$ENV{'PWD'} =~ s:\\:/:g ;
96e4d5b1	451	return $ENV{'PWD'};
	452	}
	453
	454	*_NT_cwd = \&_win32_cwd if (!defined &_NT_cwd &&
2d7a9237	455	defined &Win32::GetCwd);
96e4d5b1	456
96e4d5b1	457	*_NT_cwd = \&_os2_cwd unless defined &_NT_cwd;
68dc0745	458
39e571d4	459	sub _dos_cwd {
	460	if (!defined &Dos::GetCwd) {
	461	$ENV{'PWD'} = `command /c cd`;
	462	chop $ENV{'PWD'};
aa6b7957	463	$ENV{'PWD'} =~ s:\\:/:g ;
39e571d4	464	} else {
	465	$ENV{'PWD'} = Dos::GetCwd();
	466	}
55497cff	467	return $ENV{'PWD'};
	468	}
	469
7fbf1995	470	sub _qnx_cwd {
35b807ef	471	local $ENV{PATH} = '';
	472	local $ENV{CDPATH} = '';
	473	local $ENV{ENV} = '';
7fbf1995	474	$ENV{'PWD'} = `/usr/bin/fullpath -t`;
	475	chop $ENV{'PWD'};
	476	return $ENV{'PWD'};
	477	}
	478
	479	sub _qnx_abs_path {
35b807ef	480	local $ENV{PATH} = '';
	481	local $ENV{CDPATH} = '';
	482	local $ENV{ENV} = '';
fa921dc6	483	my $path = @_ ? shift : '.';
7fbf1995	484	my $realpath=`/usr/bin/fullpath -t $path`;
	485	chop $realpath;
	486	return $realpath;
	487	}
	488
ed79a026	489	sub _epoc_cwd {
	490	$ENV{'PWD'} = EPOC::getcwd();
	491	return $ENV{'PWD'};
	492	}
	493
ac1ad7f0	494	{
db376a24	495	no warnings; # assignments trigger 'subroutine redefined' warning
4633a7c4	496
ac1ad7f0	497	if ($^O eq 'VMS') {
96e4d5b1	498	*cwd = \&_vms_cwd;
	499	*getcwd = \&_vms_cwd;
	500	*fastcwd = \&_vms_cwd;
	501	*fastgetcwd = \&_vms_cwd;
	502	*abs_path = \&_vms_abs_path;
	503	*fast_abs_path = \&_vms_abs_path;
ac1ad7f0	504	}
	505	elsif ($^O eq 'NT' or $^O eq 'MSWin32') {
	506	# We assume that &_NT_cwd is defined as an XSUB or in the core.
96e4d5b1	507	*cwd = \&_NT_cwd;
	508	*getcwd = \&_NT_cwd;
	509	*fastcwd = \&_NT_cwd;
	510	*fastgetcwd = \&_NT_cwd;
	511	*abs_path = \&fast_abs_path;
cade0c02	512	*realpath = \&fast_abs_path;
ac1ad7f0	513	}
	514	elsif ($^O eq 'os2') {
	515	# sys_cwd may keep the builtin command
96e4d5b1	516	*cwd = defined &sys_cwd ? \&sys_cwd : \&_os2_cwd;
	517	*getcwd = \&cwd;
	518	*fastgetcwd = \&cwd;
	519	*fastcwd = \&cwd;
	520	*abs_path = \&fast_abs_path;
ac1ad7f0	521	}
39e571d4	522	elsif ($^O eq 'dos') {
	523	*cwd = \&_dos_cwd;
	524	*getcwd = \&_dos_cwd;
	525	*fastgetcwd = \&_dos_cwd;
	526	*fastcwd = \&_dos_cwd;
96e4d5b1	527	*abs_path = \&fast_abs_path;
ac1ad7f0	528	}
7438b6ad	529	elsif ($^O =~ m/^(?:qnx\|nto)$/ ) {
7fbf1995	530	*cwd = \&_qnx_cwd;
	531	*getcwd = \&_qnx_cwd;
	532	*fastgetcwd = \&_qnx_cwd;
	533	*fastcwd = \&_qnx_cwd;
	534	*abs_path = \&_qnx_abs_path;
	535	*fast_abs_path = \&_qnx_abs_path;
	536	}
4fabb596	537	elsif ($^O eq 'cygwin') {
1cab015a	538	*getcwd = \&cwd;
	539	*fastgetcwd = \&cwd;
	540	*fastcwd = \&cwd;
	541	*abs_path = \&fast_abs_path;
	542	}
ed79a026	543	elsif ($^O eq 'epoc') {
fa6a1c44	544	*cwd = \&_epoc_cwd;
fa6a1c44	545	*getcwd = \&_epoc_cwd;
ed79a026	546	*fastgetcwd = \&_epoc_cwd;
	547	*fastcwd = \&_epoc_cwd;
	548	*abs_path = \&fast_abs_path;
	549	}
4aecb5b5	550	elsif ($^O eq 'MacOS') {
	551	*getcwd = \&cwd;
	552	*fastgetcwd = \&cwd;
	553	*fastcwd = \&cwd;
	554	*abs_path = \&fast_abs_path;
	555	}
55497cff	556	}
4633a7c4	557
4633a7c4	558
a0d0e21e	559	1;