summaryrefslogtreecommitdiff
path: root/systems/texlive/tlnet/tlpkg/tlperl/lib/Cwd.pm
blob: 9b173c234bf85887a9d9338cbf4db05c7dffb26b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
package Cwd;
use strict;
use Exporter;


our $VERSION = '3.78';
my $xs_version = $VERSION;
$VERSION =~ tr/_//d;

our @ISA = qw/ Exporter /;
our @EXPORT = qw(cwd getcwd fastcwd fastgetcwd);
push @EXPORT, qw(getdcwd) if $^O eq 'MSWin32';
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') {
    local $^W = 0;

    *cwd                = defined &sys_cwd ? \&sys_cwd : \&_os2_cwd;
    *getcwd             = \&cwd;
    *fastgetcwd         = \&cwd;
    *fastcwd            = \&cwd;

    *fast_abs_path      = \&sys_abspath if defined &sys_abspath;
    *abs_path           = \&fast_abs_path;
    *realpath           = \&fast_abs_path;
    *fast_realpath      = \&fast_abs_path;

    return 1;
}

# Need to look up the feature settings on VMS.  The preferred way is to use the
# VMS::Feature module, but that may not be available to dual life modules.

my $use_vms_feature;
BEGIN {
    if ($^O eq 'VMS') {
        if (eval { local $SIG{__DIE__};
                   local @INC = @INC;
                   pop @INC if $INC[-1] eq '.';
                   require VMS::Feature; }) {
            $use_vms_feature = 1;
        }
    }
}

# Need to look up the UNIX report mode.  This may become a dynamic mode
# in the future.
sub _vms_unix_rpt {
    my $unix_rpt;
    if ($use_vms_feature) {
        $unix_rpt = VMS::Feature::current("filename_unix_report");
    } else {
        my $env_unix_rpt = $ENV{'DECC$FILENAME_UNIX_REPORT'} || '';
        $unix_rpt = $env_unix_rpt =~ /^[ET1]/i; 
    }
    return $unix_rpt;
}

# Need to look up the EFS character set mode.  This may become a dynamic
# mode in the future.
sub _vms_efs {
    my $efs;
    if ($use_vms_feature) {
        $efs = VMS::Feature::current("efs_charset");
    } else {
        my $env_efs = $ENV{'DECC$EFS_CHARSET'} || '';
        $efs = $env_efs =~ /^[ET1]/i; 
    }
    return $efs;
}


# If loading the XS stuff doesn't work, we can fall back to pure perl
if(! defined &getcwd && defined &DynaLoader::boot_DynaLoader) { # skipped on miniperl
    require XSLoader;
    XSLoader::load( __PACKAGE__, $xs_version);
}

# Big nasty table of function aliases
my %METHOD_MAP =
  (
   VMS =>
   {
    cwd			=> '_vms_cwd',
    getcwd		=> '_vms_cwd',
    fastcwd		=> '_vms_cwd',
    fastgetcwd		=> '_vms_cwd',
    abs_path		=> '_vms_abs_path',
    fast_abs_path	=> '_vms_abs_path',
   },

   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',
   },

   dos => 
   {
    cwd			=> '_dos_cwd',
    getcwd		=> '_dos_cwd',
    fastgetcwd		=> '_dos_cwd',
    fastcwd		=> '_dos_cwd',
    abs_path		=> 'fast_abs_path',
   },

   # QNX4.  QNX6 has a $os of 'nto'.
   qnx =>
   {
    cwd			=> '_qnx_cwd',
    getcwd		=> '_qnx_cwd',
    fastgetcwd		=> '_qnx_cwd',
    fastcwd		=> '_qnx_cwd',
    abs_path		=> '_qnx_abs_path',
    fast_abs_path	=> '_qnx_abs_path',
   },

   cygwin =>
   {
    getcwd		=> 'cwd',
    fastgetcwd		=> 'cwd',
    fastcwd		=> 'cwd',
    abs_path		=> 'fast_abs_path',
    realpath		=> 'fast_abs_path',
   },

   amigaos =>
   {
    getcwd              => '_backtick_pwd',
    fastgetcwd          => '_backtick_pwd',
    fastcwd             => '_backtick_pwd',
    abs_path            => 'fast_abs_path',
   }
  );

$METHOD_MAP{NT} = $METHOD_MAP{MSWin32};


# 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 $pwd_cmd;
if($^O ne 'MSWin32') {
    foreach my $try ('/bin/pwd',
		     '/usr/bin/pwd',
		     '/QOpenSys/bin/pwd', # OS/400 PASE.
		    ) {
	if( -x $try ) {
	    $pwd_cmd = $try;
	    last;
	}
    }
}

# Android has a built-in pwd. Using $pwd_cmd will DTRT if
# this perl was compiled with -Dd_useshellcmds, which is the
# default for Android, but the block below is needed for the
# miniperl running on the host when cross-compiling, and
# potentially for native builds with -Ud_useshellcmds.
if ($^O =~ /android/) {
    # If targetsh is executable, then we're either a full
    # perl, or a miniperl for a native build.
    if ( exists($Config::Config{targetsh}) && -x $Config::Config{targetsh}) {
        $pwd_cmd = "$Config::Config{targetsh} -c pwd"
    }
    else {
        my $sh = $Config::Config{sh} || (-x '/system/bin/sh' ? '/system/bin/sh' : 'sh');
        $pwd_cmd = "$sh -c pwd"
    }
}

my $found_pwd_cmd = defined($pwd_cmd);
unless ($pwd_cmd) {
    # Isn't this wrong?  _backtick_pwd() will fail if someone has
    # pwd in their path but it is not /bin/pwd or /usr/bin/pwd?
    # See [perl #16774]. --jhi
    $pwd_cmd = 'pwd';
}

# Lazy-load Carp
sub _carp  { require Carp; Carp::carp(@_)  }
sub _croak { require Carp; Carp::croak(@_) }

# The 'natural and safe form' for UNIX (pwd may be setuid root)
sub _backtick_pwd {

    # Localize %ENV entries in a way that won't create new hash keys.
    # Under AmigaOS we don't want to localize as it stops perl from
    # finding 'sh' in the PATH.
    my @localize = grep exists $ENV{$_}, qw(PATH IFS CDPATH ENV BASH_ENV) if $^O ne "amigaos";
    local @ENV{@localize} if @localize;
    
    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 ($METHOD_MAP{$^O}{cwd} or defined &cwd) {
    # The pwd command is not available in some chroot(2)'ed environments
    my $sep = $Config::Config{path_sep} || ':';
    my $os = $^O;  # Protect $^O from tainting


    # Try again to find a pwd, this time searching the whole PATH.
    if (defined $ENV{PATH} and $os ne 'MSWin32') {  # no pwd on Windows
	my @candidates = split($sep, $ENV{PATH});
	while (!$found_pwd_cmd and @candidates) {
	    my $candidate = shift @candidates;
	    $found_pwd_cmd = 1 if -x "$candidate/pwd";
	}
    }

    if( $found_pwd_cmd )
    {
	*cwd = \&_backtick_pwd;
    }
    else {
	*cwd = \&getcwd;
    }
}

if ($^O eq 'cygwin') {
  # We need to make sure cwd() is called with no args, because it's
  # got an arg-less prototype and will die if args are present.
  local $^W = 0;
  my $orig_cwd = \&cwd;
  *cwd = sub { &$orig_cwd() }
}


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

# A non-XS version of getcwd() - also used to bootstrap the perl build
# process, when miniperl is running and no XS loading happens.
sub _perl_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.
    # Untaint it then check that we landed where we started.
    $path =~ /^(.*)\z/s		# untaint
	&& CORE::chdir($1) or return undef;
    ($cdev, $cino) = stat('.');
    die "Unstable directory path, current directory changed unexpectedly"
	if $cdev != $orig_cdev || $cino != $orig_cino;
    $path;
}
if (not defined &fastcwd) { *fastcwd = \&fastcwd_ }


# 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 $newdir = @_ ? shift : '';	# allow for no arg (chdir to HOME dir)
    if ($^O eq "cygwin") {
      $newdir =~ s|\A///+|//|;
      $newdir =~ s|(?<=[^/])//+|/|g;
    }
    elsif ($^O ne 'MSWin32') {
      $newdir =~ s|///*|/|g;
    }
    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 'MSWin32') {
	$ENV{'PWD'} = $newpwd;
	return 1;
    }

    if (ref $newdir eq 'GLOB') { # in case a file/dir handle is passed in
	$ENV{'PWD'} = cwd();
    } elsif ($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;
}


sub _perl_abs_path
{
    my $start = @_ ? shift : '.';
    my($dotdots, $cwd, @pst, @cst, $dir, @tst);

    unless (@cst = stat( $start ))
    {
	return undef;
    }

    unless (-d _) {
        # Make sure we can be invoked on plain files, not just directories.
        # NOTE that this routine assumes that '/' is the only directory separator.
	
        my ($dir, $file) = $start =~ m{^(.*)/(.+)$}
	    or return cwd() . '/' . $start;
	
	# Can't use "-l _" here, because the previous stat was a stat(), not an lstat().
	if (-l $start) {
	    my $link_target = readlink($start);
	    die "Can't resolve link $start: $!" unless defined $link_target;
	    
	    require File::Spec;
            $link_target = $dir . '/' . $link_target
                unless File::Spec->file_name_is_absolute($link_target);
	    
	    return abs_path($link_target);
	}
	
	return $dir ? abs_path($dir) . "/$file" : "/$file";
    }

    $cwd = '';
    $dotdots = $start;
    do
    {
	$dotdots .= '/..';
	@pst = @cst;
	local *PARENT;
	unless (opendir(PARENT, $dotdots))
	{
	    return undef;
	}
	unless (@cst = stat($dotdots))
	{
	    my $e = $!;
	    closedir(PARENT);
	    $! = $e;
	    return undef;
	}
	if ($pst[0] == $cst[0] && $pst[1] == $cst[1])
	{
	    $dir = undef;
	}
	else
	{
	    do
	    {
		unless (defined ($dir = readdir(PARENT)))
	        {
		    closedir(PARENT);
		    require Errno;
		    $! = Errno::ENOENT();
		    return undef;
		}
		$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;
}


my $Curdir;
sub fast_abs_path {
    local $ENV{PWD} = $ENV{PWD} || ''; # Guard against clobberage
    my $cwd = getcwd();
    defined $cwd or return undef;
    require File::Spec;
    my $path = @_ ? shift : ($Curdir ||= File::Spec->curdir);

    # Detaint else we'll explode in taint mode.  This is safe because
    # we're not doing anything dangerous with it.
    ($path) = $path =~ /(.*)/s;
    ($cwd)  = $cwd  =~ /(.*)/s;

    unless (-e $path) {
	require Errno;
	$! = Errno::ENOENT();
	return undef;
    }

    unless (-d _) {
        # Make sure we can be invoked on plain files, not just directories.
	
	my ($vol, $dir, $file) = File::Spec->splitpath($path);
	return File::Spec->catfile($cwd, $path) unless length $dir;

	if (-l $path) {
	    my $link_target = readlink($path);
	    defined $link_target or return undef;
	    
	    $link_target = File::Spec->catpath($vol, $dir, $link_target)
                unless File::Spec->file_name_is_absolute($link_target);
	    
	    return fast_abs_path($link_target);
	}
	
	return $dir eq File::Spec->rootdir
	  ? File::Spec->catpath($vol, $dir, $file)
	  : fast_abs_path(File::Spec->catpath($vol, $dir, '')) . '/' . $file;
    }

    if (!CORE::chdir($path)) {
	return undef;
    }
    my $realpath = getcwd();
    if (! ((-d $cwd) && (CORE::chdir($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 = shift;

    my $efs = _vms_efs;
    my $unix_rpt = _vms_unix_rpt;

    if (defined &VMS::Filespec::vmsrealpath) {
        my $path_unix = 0;
        my $path_vms = 0;

        $path_unix = 1 if ($path =~ m#(?<=\^)/#);
        $path_unix = 1 if ($path =~ /^\.\.?$/);
        $path_vms = 1 if ($path =~ m#[\[<\]]#);
        $path_vms = 1 if ($path =~ /^--?$/);

        my $unix_mode = $path_unix;
        if ($efs) {
            # In case of a tie, the Unix report mode decides.
            if ($path_vms == $path_unix) {
                $unix_mode = $unix_rpt;
            } else {
                $unix_mode = 0 if $path_vms;
            }
        }

        if ($unix_mode) {
            # Unix format
            return VMS::Filespec::unixrealpath($path);
        }

	# VMS format

	my $new_path = VMS::Filespec::vmsrealpath($path);

	# Perl expects directories to be in directory format
	$new_path = VMS::Filespec::pathify($new_path) if -d $path;
	return $new_path;
    }

    # Fallback to older algorithm if correct ones are not
    # available.

    if (-l $path) {
        my $link_target = readlink($path);
        die "Can't resolve link $path: $!" unless defined $link_target;

        return _vms_abs_path($link_target);
    }

    # may need to turn foo.dir into [.foo]
    my $pathified = VMS::Filespec::pathify($path);
    $path = $pathified if defined $pathified;
	
    return VMS::Filespec::rmsexpand($path);
}

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

sub _win32_cwd_simple {
    my $pwd = `cd`;
    chomp $pwd;
    $pwd =~ s:\\:/:g ;
    $ENV{'PWD'} = $pwd;
    return $pwd;
}

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

*_NT_cwd = defined &Win32::GetCwd ? \&_win32_cwd : \&_win32_cwd_simple;

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

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

sub _qnx_abs_path {
	local $ENV{PATH} = '';
	local $ENV{CDPATH} = '';
	local $ENV{ENV} = '';
    my $path = @_ ? shift : '.';
    local *REALPATH;

    defined( open(REALPATH, '-|') || exec '/usr/bin/fullpath', '-t', $path ) or
      die "Can't open /usr/bin/fullpath: $!";
    my $realpath = <REALPATH>;
    close REALPATH;
    chomp $realpath;
    return $realpath;
}

# Now that all the base-level functions are set up, alias the
# user-level functions to the right places

if (exists $METHOD_MAP{$^O}) {
  my $map = $METHOD_MAP{$^O};
  foreach my $name (keys %$map) {
    local $^W = 0;  # assignments trigger 'subroutine redefined' warning
    no strict 'refs';
    *{$name} = \&{$map->{$name}};
  }
}

# built-in from 5.30
*getcwd = \&Internals::getcwd
  if !defined &getcwd && defined &Internals::getcwd;

# In case the XS version doesn't load.
*abs_path = \&_perl_abs_path unless defined &abs_path;
*getcwd = \&_perl_getcwd unless defined &getcwd;

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

1;
__END__

=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() (and, on Win32, getdcwd()) 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.  On error returns C<undef>,
with C<$!> set to indicate the error.

Exposes the POSIX function getcwd(3) or re-implements it if it's not
available.

=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).

=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().

=item getdcwd

    my $cwd = getdcwd();
    my $cwd = getdcwd('C:');

The getdcwd() function is also provided on Win32 to get the current working
directory on the specified drive, since Windows maintains a separate current
working directory for each drive.  If no drive is specified then the current
drive is assumed.

This function simply calls the Microsoft C library _getdcwd() function.

=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.  If no argument is
given they'll use the current working directory.

=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).  On error returns C<undef>, with C<$!>
set to indicate the error.

=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 separators 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 AUTHOR

Originally by the perl5-porters.

Maintained by Ken Williams <KWILLIAMS@cpan.org>

=head1 COPYRIGHT

Copyright (c) 2004 by the Perl 5 Porters.  All rights reserved.

This program is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.

Portions of the C code in this library are copyright (c) 1994 by the
Regents of the University of California.  All rights reserved.  The
license on this code is compatible with the licensing of the rest of
the distribution - please see the source code in F<Cwd.xs> for the
details.

=head1 SEE ALSO

L<File::chdir>

=cut