[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 $abs_path = abs_path($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`;
    # `pwd` may fail e.g. if the disk is full
    local $/ = "\n";
    chomp($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($^O eq 'MacOS' || grep { -x "$_/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 {
    $ENV{'PWD'} = `/usr/bin/fullpath -t`;
    chop $ENV{'PWD'};
    return $ENV{'PWD'};
}

sub _qnx_abs_path {
    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
	98	my $abs_path = abs_path($file);
	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`;
7e03f963	191	# `pwd` may fail e.g. if the disk is full
5cf6da5f	192	local $/ = "\n";
7e03f963	193	chomp($cwd) if defined $cwd;
4633a7c4	194	$cwd;
8b88ae92	195	}
4633a7c4	196
	197	# Since some ports may predefine cwd internally (e.g., NT)
	198	# we take care not to override an existing definition for cwd().
	199
ea54c8bd	200	unless(defined &cwd) {
ea54c8bd	201	# The pwd command is not available in some chroot(2)'ed environments
4aecb5b5	202	if($^O eq 'MacOS' \|\| grep { -x "$_/pwd" } split(':', $ENV{PATH})) {
ea54c8bd	203	*cwd = \&_backtick_pwd;
	204	}
	205	else {
	206	*cwd = \&getcwd;
	207	}
	208	}
a0d0e21e	209
1f4f94f5	210	# set a reasonable (and very safe) default for fastgetcwd, in case it
	211	# isn't redefined later (20001212 rspier)
	212	*fastgetcwd = \&cwd;
748a9306	213
a0d0e21e	214	# By Brandon S. Allbery
	215	#
	216	# Usage: $cwd = getcwd();
	217
	218	sub getcwd
	219	{
07569ed3	220	abs_path('.');
a0d0e21e	221	}
a0d0e21e	222
a0c9c202	223
	224	# By John Bazik
	225	#
	226	# Usage: $cwd = &fastcwd;
	227	#
	228	# This is a faster version of getcwd. It's also more dangerous because
	229	# you might chdir out of a directory that you can't chdir back into.
	230
	231	sub fastcwd {
	232	my($odev, $oino, $cdev, $cino, $tdev, $tino);
	233	my(@path, $path);
	234	local(*DIR);
	235
	236	my($orig_cdev, $orig_cino) = stat('.');
	237	($cdev, $cino) = ($orig_cdev, $orig_cino);
	238	for (;;) {
	239	my $direntry;
	240	($odev, $oino) = ($cdev, $cino);
	241	CORE::chdir('..') \|\| return undef;
	242	($cdev, $cino) = stat('.');
	243	last if $odev == $cdev && $oino == $cino;
	244	opendir(DIR, '.') \|\| return undef;
	245	for (;;) {
	246	$direntry = readdir(DIR);
	247	last unless defined $direntry;
	248	next if $direntry eq '.';
	249	next if $direntry eq '..';
	250
	251	($tdev, $tino) = lstat($direntry);
	252	last unless $tdev != $odev \|\| $tino != $oino;
	253	}
	254	closedir(DIR);
	255	return undef unless defined $direntry; # should never happen
	256	unshift(@path, $direntry);
	257	}
	258	$path = '/' . join('/', @path);
	259	if ($^O eq 'apollo') { $path = "/".$path; }
	260	# At this point $path may be tainted (if tainting) and chdir would fail.
	261	# To be more useful we untaint it then check that we landed where we started.
	262	$path = $1 if $path =~ /^(.*)\z/s; # untaint
	263	CORE::chdir($path) \|\| return undef;
	264	($cdev, $cino) = stat('.');
	265	die "Unstable directory path, current directory changed unexpectedly"
	266	if $cdev != $orig_cdev \|\| $cino != $orig_cino;
	267	$path;
	268	}
	269
	270
4633a7c4	271	# Keeps track of current working directory in PWD environment var
a0d0e21e	272	# Usage:
	273	# use Cwd 'chdir';
	274	# chdir $newdir;
	275
4633a7c4	276	my $chdir_init = 0;
a0d0e21e	277
4633a7c4	278	sub chdir_init {
3b8e3443	279	if ($ENV{'PWD'} and $^O ne 'os2' and $^O ne 'dos' and $^O ne 'MSWin32') {
a0d0e21e	280	my($dd,$di) = stat('.');
	281	my($pd,$pi) = stat($ENV{'PWD'});
	282	if (!defined $dd or !defined $pd or $di != $pi or $dd != $pd) {
4633a7c4	283	$ENV{'PWD'} = cwd();
a0d0e21e	284	}
	285	}
	286	else {
3b8e3443	287	my $wd = cwd();
	288	$wd = Win32::GetFullPathName($wd) if $^O eq 'MSWin32';
	289	$ENV{'PWD'} = $wd;
a0d0e21e	290	}
4633a7c4	291	# Strip an automounter prefix (where /tmp_mnt/foo/bar == /foo/bar)
3b8e3443	292	if ($^O ne 'MSWin32' and $ENV{'PWD'} =~ m\|(/[^/]+(/[^/]+/[^/]+))(.*)\|s) {
a0d0e21e	293	my($pd,$pi) = stat($2);
	294	my($dd,$di) = stat($1);
	295	if (defined $pd and defined $dd and $di == $pi and $dd == $pd) {
	296	$ENV{'PWD'}="$2$3";
	297	}
	298	}
	299	$chdir_init = 1;
	300	}
	301
	302	sub chdir {
22978713	303	my $newdir = @_ ? shift : ''; # allow for no arg (chdir to HOME dir)
3b8e3443	304	$newdir =~ s\|///*\|/\|g unless $^O eq 'MSWin32';
a0d0e21e	305	chdir_init() unless $chdir_init;
4ffa1610	306	my $newpwd;
	307	if ($^O eq 'MSWin32') {
	308	# get the full path name before the chdir()
	309	$newpwd = Win32::GetFullPathName($newdir);
	310	}
	311
4633a7c4	312	return 0 unless CORE::chdir $newdir;
4ffa1610	313
3b8e3443	314	if ($^O eq 'VMS') {
	315	return $ENV{'PWD'} = $ENV{'DEFAULT'}
	316	}
4aecb5b5	317	elsif ($^O eq 'MacOS') {
	318	return $ENV{'PWD'} = cwd();
	319	}
3b8e3443	320	elsif ($^O eq 'MSWin32') {
4ffa1610	321	$ENV{'PWD'} = $newpwd;
3b8e3443	322	return 1;
3b8e3443	323	}
748a9306	324
392d8ab8	325	if ($newdir =~ m#^/#s) {
a0d0e21e	326	$ENV{'PWD'} = $newdir;
4633a7c4	327	} else {
	328	my @curdir = split(m#/#,$ENV{'PWD'});
	329	@curdir = ('') unless @curdir;
	330	my $component;
a0d0e21e	331	foreach $component (split(m#/#, $newdir)) {
	332	next if $component eq '.';
	333	pop(@curdir),next if $component eq '..';
	334	push(@curdir,$component);
	335	}
	336	$ENV{'PWD'} = join('/',@curdir) \|\| '/';
	337	}
4633a7c4	338	1;
a0d0e21e	339	}
a0d0e21e	340
a0c9c202	341
	342	# In case the XS version doesn't load.
	343	*abs_path = \&_perl_abs_path unless defined &abs_path;
	344	sub _perl_abs_path
	345	{
	346	my $start = @_ ? shift : '.';
	347	my($dotdots, $cwd, @pst, @cst, $dir, @tst);
	348
	349	unless (@cst = stat( $start ))
	350	{
	351	carp "stat($start): $!";
	352	return '';
	353	}
	354	$cwd = '';
	355	$dotdots = $start;
	356	do
	357	{
	358	$dotdots .= '/..';
	359	@pst = @cst;
	360	unless (opendir(PARENT, $dotdots))
	361	{
	362	carp "opendir($dotdots): $!";
	363	return '';
	364	}
	365	unless (@cst = stat($dotdots))
	366	{
	367	carp "stat($dotdots): $!";
	368	closedir(PARENT);
	369	return '';
	370	}
	371	if ($pst[0] == $cst[0] && $pst[1] == $cst[1])
	372	{
	373	$dir = undef;
	374	}
	375	else
	376	{
	377	do
	378	{
	379	unless (defined ($dir = readdir(PARENT)))
	380	{
	381	carp "readdir($dotdots): $!";
	382	closedir(PARENT);
	383	return '';
	384	}
	385	$tst[0] = $pst[0]+1 unless (@tst = lstat("$dotdots/$dir"))
	386	}
	387	while ($dir eq '.' \|\| $dir eq '..' \|\| $tst[0] != $pst[0] \|\|
	388	$tst[1] != $pst[1]);
	389	}
	390	$cwd = (defined $dir ? "$dir" : "" ) . "/$cwd" ;
	391	closedir(PARENT);
	392	} while (defined $dir);
	393	chop($cwd) unless $cwd eq '/'; # drop the trailing /
	394	$cwd;
	395	}
	396
	397
e4c51978	398	# added function alias for those of us more
	399	# used to the libc function. --tchrist 27-Jan-00
	400	*realpath = \&abs_path;
	401
96e4d5b1	402	sub fast_abs_path {
96e4d5b1	403	my $cwd = getcwd();
4d6b4052	404	require File::Spec;
4d6b4052	405	my $path = @_ ? shift : File::Spec->curdir;
e79e61e4	406	CORE::chdir($path) \|\| croak "Cannot chdir to $path:$!";
96e4d5b1	407	my $realpath = getcwd();
e79e61e4	408	CORE::chdir($cwd) \|\| croak "Cannot chdir back to $cwd:$!";
96e4d5b1	409	$realpath;
8b88ae92	410	}
8b88ae92	411
e4c51978	412	# added function alias to follow principle of least surprise
	413	# based on previous aliasing. --tchrist 27-Jan-00
	414	*fast_realpath = \&fast_abs_path;
	415
4633a7c4	416
	417	# --- PORTING SECTION ---
	418
	419	# VMS: $ENV{'DEFAULT'} points to default directory at all times
bd3fa61c	420	# 06-Mar-1996 Charles Bailey bailey@newman.upenn.edu
c6538b72	421	# Note: Use of Cwd::chdir() causes the logical name PWD to be defined
8b88ae92	422	# in the process logical name table as the default device and directory
8b88ae92	423	# seen by Perl. This may not be the same as the default device
4633a7c4	424	# and directory seen by DCL after Perl exits, since the effects
4633a7c4	425	# the CRTL chdir() function persist only until Perl exits.
4633a7c4	426
4633a7c4	427	sub _vms_cwd {
96e4d5b1	428	return $ENV{'DEFAULT'};
	429	}
	430
	431	sub _vms_abs_path {
	432	return $ENV{'DEFAULT'} unless @_;
	433	my $path = VMS::Filespec::pathify($_[0]);
	434	croak("Invalid path name $_[0]") unless defined $path;
	435	return VMS::Filespec::rmsexpand($path);
4633a7c4	436	}
68dc0745	437
4633a7c4	438	sub _os2_cwd {
	439	$ENV{'PWD'} = `cmd /c cd`;
	440	chop $ENV{'PWD'};
aa6b7957	441	$ENV{'PWD'} =~ s:\\:/:g ;
4633a7c4	442	return $ENV{'PWD'};
	443	}
	444
96e4d5b1	445	sub _win32_cwd {
2d7a9237	446	$ENV{'PWD'} = Win32::GetCwd();
aa6b7957	447	$ENV{'PWD'} =~ s:\\:/:g ;
96e4d5b1	448	return $ENV{'PWD'};
	449	}
	450
	451	*_NT_cwd = \&_win32_cwd if (!defined &_NT_cwd &&
2d7a9237	452	defined &Win32::GetCwd);
96e4d5b1	453
96e4d5b1	454	*_NT_cwd = \&_os2_cwd unless defined &_NT_cwd;
68dc0745	455
39e571d4	456	sub _dos_cwd {
	457	if (!defined &Dos::GetCwd) {
	458	$ENV{'PWD'} = `command /c cd`;
	459	chop $ENV{'PWD'};
aa6b7957	460	$ENV{'PWD'} =~ s:\\:/:g ;
39e571d4	461	} else {
	462	$ENV{'PWD'} = Dos::GetCwd();
	463	}
55497cff	464	return $ENV{'PWD'};
	465	}
	466
7fbf1995	467	sub _qnx_cwd {
	468	$ENV{'PWD'} = `/usr/bin/fullpath -t`;
	469	chop $ENV{'PWD'};
	470	return $ENV{'PWD'};
	471	}
	472
	473	sub _qnx_abs_path {
fa921dc6	474	my $path = @_ ? shift : '.';
7fbf1995	475	my $realpath=`/usr/bin/fullpath -t $path`;
	476	chop $realpath;
	477	return $realpath;
	478	}
	479
ed79a026	480	sub _epoc_cwd {
	481	$ENV{'PWD'} = EPOC::getcwd();
	482	return $ENV{'PWD'};
	483	}
	484
ac1ad7f0	485	{
db376a24	486	no warnings; # assignments trigger 'subroutine redefined' warning
4633a7c4	487
ac1ad7f0	488	if ($^O eq 'VMS') {
96e4d5b1	489	*cwd = \&_vms_cwd;
	490	*getcwd = \&_vms_cwd;
	491	*fastcwd = \&_vms_cwd;
	492	*fastgetcwd = \&_vms_cwd;
	493	*abs_path = \&_vms_abs_path;
	494	*fast_abs_path = \&_vms_abs_path;
ac1ad7f0	495	}
	496	elsif ($^O eq 'NT' or $^O eq 'MSWin32') {
	497	# We assume that &_NT_cwd is defined as an XSUB or in the core.
96e4d5b1	498	*cwd = \&_NT_cwd;
	499	*getcwd = \&_NT_cwd;
	500	*fastcwd = \&_NT_cwd;
	501	*fastgetcwd = \&_NT_cwd;
	502	*abs_path = \&fast_abs_path;
cade0c02	503	*realpath = \&fast_abs_path;
ac1ad7f0	504	}
	505	elsif ($^O eq 'os2') {
	506	# sys_cwd may keep the builtin command
96e4d5b1	507	*cwd = defined &sys_cwd ? \&sys_cwd : \&_os2_cwd;
	508	*getcwd = \&cwd;
	509	*fastgetcwd = \&cwd;
	510	*fastcwd = \&cwd;
	511	*abs_path = \&fast_abs_path;
ac1ad7f0	512	}
39e571d4	513	elsif ($^O eq 'dos') {
	514	*cwd = \&_dos_cwd;
	515	*getcwd = \&_dos_cwd;
	516	*fastgetcwd = \&_dos_cwd;
	517	*fastcwd = \&_dos_cwd;
96e4d5b1	518	*abs_path = \&fast_abs_path;
ac1ad7f0	519	}
7438b6ad	520	elsif ($^O =~ m/^(?:qnx\|nto)$/ ) {
7fbf1995	521	*cwd = \&_qnx_cwd;
	522	*getcwd = \&_qnx_cwd;
	523	*fastgetcwd = \&_qnx_cwd;
	524	*fastcwd = \&_qnx_cwd;
	525	*abs_path = \&_qnx_abs_path;
	526	*fast_abs_path = \&_qnx_abs_path;
	527	}
4fabb596	528	elsif ($^O eq 'cygwin') {
1cab015a	529	*getcwd = \&cwd;
	530	*fastgetcwd = \&cwd;
	531	*fastcwd = \&cwd;
	532	*abs_path = \&fast_abs_path;
	533	}
ed79a026	534	elsif ($^O eq 'epoc') {
fa6a1c44	535	*cwd = \&_epoc_cwd;
fa6a1c44	536	*getcwd = \&_epoc_cwd;
ed79a026	537	*fastgetcwd = \&_epoc_cwd;
	538	*fastcwd = \&_epoc_cwd;
	539	*abs_path = \&fast_abs_path;
	540	}
4aecb5b5	541	elsif ($^O eq 'MacOS') {
	542	*getcwd = \&cwd;
	543	*fastgetcwd = \&cwd;
	544	*fastcwd = \&cwd;
	545	*abs_path = \&fast_abs_path;
	546	}
55497cff	547	}
4633a7c4	548
4633a7c4	549
a0d0e21e	550	1;