6 getcwd - get pathname of current working directory
23 use Cwd 'abs_path'; # aka realpath()
24 print abs_path($ENV{'PWD'});
26 use Cwd 'fast_abs_path';
27 print fast_abs_path($ENV{'PWD'});
31 The getcwd() function re-implements the getcwd(3) (or getwd(3)) functions
34 The abs_path() function takes a single argument and returns the
35 absolute pathname for that argument. It uses the same algorithm
36 as getcwd(). (Actually, getcwd() is abs_path(".")) Symbolic links
37 and relative-path components ("." and "..") are resolved to return
38 the canonical pathname, just like realpath(3). Also callable as
41 The fastcwd() function looks the same as getcwd(), but runs faster.
42 It's also more dangerous because it might conceivably chdir() you out
43 of a directory that it can't chdir() you back into. If fastcwd
44 encounters a problem it will return undef but will probably leave you
45 in a different directory. For a measure of extra security, if
46 everything appears to have worked, the fastcwd() function will check
47 that it leaves you in the same directory that it started in. If it has
48 changed it will C<die> with the message "Unstable directory path,
49 current directory changed unexpectedly". That should never happen.
51 The fast_abs_path() function looks the same as abs_path(), but runs faster.
52 And like fastcwd() is more dangerous.
54 The cwd() function looks the same as getcwd and fastgetcwd but is
55 implemented using the most natural and safe form for the current
56 architecture. For most systems it is identical to `pwd` (but without
57 the trailing line terminator).
59 It is recommended that cwd (or another *cwd() function) is used in
60 I<all> code to ensure portability.
62 If you ask to override your chdir() built-in function, then your PWD
63 environment variable will be kept up to date. (See
64 L<perlsub/Overriding Builtin Functions>.) Note that it will only be
65 kept up to date if all packages which use chdir import it from Cwd.
77 @EXPORT = qw(cwd getcwd fastcwd fastgetcwd);
78 @EXPORT_OK = qw(chdir abs_path fast_abs_path realpath fast_realpath);
81 # The 'natural and safe form' for UNIX (pwd may be setuid root)
85 # `pwd` may fail e.g. if the disk is full
86 chomp($cwd) if defined $cwd;
90 # Since some ports may predefine cwd internally (e.g., NT)
91 # we take care not to override an existing definition for cwd().
93 *cwd = \&_backtick_pwd unless defined &cwd;
96 # By Brandon S. Allbery
98 # Usage: $cwd = getcwd();
107 # Usage: $cwd = &fastcwd;
109 # This is a faster version of getcwd. It's also more dangerous because
110 # you might chdir out of a directory that you can't chdir back into.
113 my($odev, $oino, $cdev, $cino, $tdev, $tino);
117 my($orig_cdev, $orig_cino) = stat('.');
118 ($cdev, $cino) = ($orig_cdev, $orig_cino);
121 ($odev, $oino) = ($cdev, $cino);
122 CORE::chdir('..') || return undef;
123 ($cdev, $cino) = stat('.');
124 last if $odev == $cdev && $oino == $cino;
125 opendir(DIR, '.') || return undef;
127 $direntry = readdir(DIR);
128 last unless defined $direntry;
129 next if $direntry eq '.';
130 next if $direntry eq '..';
132 ($tdev, $tino) = lstat($direntry);
133 last unless $tdev != $odev || $tino != $oino;
136 return undef unless defined $direntry; # should never happen
137 unshift(@path, $direntry);
139 $path = '/' . join('/', @path);
140 if ($^O eq 'apollo') { $path = "/".$path; }
141 # At this point $path may be tainted (if tainting) and chdir would fail.
142 # To be more useful we untaint it then check that we landed where we started.
143 $path = $1 if $path =~ /^(.*)\z/s; # untaint
144 CORE::chdir($path) || return undef;
145 ($cdev, $cino) = stat('.');
146 die "Unstable directory path, current directory changed unexpectedly"
147 if $cdev != $orig_cdev || $cino != $orig_cino;
152 # Keeps track of current working directory in PWD environment var
160 if ($ENV{'PWD'} and $^O ne 'os2' and $^O ne 'dos') {
161 my($dd,$di) = stat('.');
162 my($pd,$pi) = stat($ENV{'PWD'});
163 if (!defined $dd or !defined $pd or $di != $pi or $dd != $pd) {
170 # Strip an automounter prefix (where /tmp_mnt/foo/bar == /foo/bar)
171 if ($ENV{'PWD'} =~ m|(/[^/]+(/[^/]+/[^/]+))(.*)|s) {
172 my($pd,$pi) = stat($2);
173 my($dd,$di) = stat($1);
174 if (defined $pd and defined $dd and $di == $pi and $dd == $pd) {
182 my $newdir = shift || ''; # allow for no arg (chdir to HOME dir)
183 $newdir =~ s|///*|/|g;
184 chdir_init() unless $chdir_init;
185 return 0 unless CORE::chdir $newdir;
186 if ($^O eq 'VMS') { return $ENV{'PWD'} = $ENV{'DEFAULT'} }
188 if ($newdir =~ m#^/#s) {
189 $ENV{'PWD'} = $newdir;
191 my @curdir = split(m#/#,$ENV{'PWD'});
192 @curdir = ('') unless @curdir;
194 foreach $component (split(m#/#, $newdir)) {
195 next if $component eq '.';
196 pop(@curdir),next if $component eq '..';
197 push(@curdir,$component);
199 $ENV{'PWD'} = join('/',@curdir) || '/';
204 # Taken from Cwd.pm It is really getcwd with an optional
205 # parameter instead of '.'
210 my $start = @_ ? shift : '.';
211 my($dotdots, $cwd, @pst, @cst, $dir, @tst);
213 unless (@cst = stat( $start ))
215 carp "stat($start): $!";
224 unless (opendir(PARENT, $dotdots))
226 carp "opendir($dotdots): $!";
229 unless (@cst = stat($dotdots))
231 carp "stat($dotdots): $!";
235 if ($pst[0] == $cst[0] && $pst[1] == $cst[1])
243 unless (defined ($dir = readdir(PARENT)))
245 carp "readdir($dotdots): $!";
249 $tst[0] = $pst[0]+1 unless (@tst = lstat("$dotdots/$dir"))
251 while ($dir eq '.' || $dir eq '..' || $tst[0] != $pst[0] ||
254 $cwd = (defined $dir ? "$dir" : "" ) . "/$cwd" ;
256 } while (defined $dir);
257 chop($cwd) unless $cwd eq '/'; # drop the trailing /
261 # added function alias for those of us more
262 # used to the libc function. --tchrist 27-Jan-00
263 *realpath = \&abs_path;
267 my $path = shift || '.';
268 CORE::chdir($path) || croak "Cannot chdir to $path:$!";
269 my $realpath = getcwd();
270 CORE::chdir($cwd) || croak "Cannot chdir back to $cwd:$!";
274 # added function alias to follow principle of least surprise
275 # based on previous aliasing. --tchrist 27-Jan-00
276 *fast_realpath = \&fast_abs_path;
279 # --- PORTING SECTION ---
281 # VMS: $ENV{'DEFAULT'} points to default directory at all times
282 # 06-Mar-1996 Charles Bailey bailey@newman.upenn.edu
283 # Note: Use of Cwd::chdir() causes the logical name PWD to be defined
284 # in the process logical name table as the default device and directory
285 # seen by Perl. This may not be the same as the default device
286 # and directory seen by DCL after Perl exits, since the effects
287 # the CRTL chdir() function persist only until Perl exits.
290 return $ENV{'DEFAULT'};
294 return $ENV{'DEFAULT'} unless @_;
295 my $path = VMS::Filespec::pathify($_[0]);
296 croak("Invalid path name $_[0]") unless defined $path;
297 return VMS::Filespec::rmsexpand($path);
301 $ENV{'PWD'} = `cmd /c cd`;
303 $ENV{'PWD'} =~ s:\\:/:g ;
308 $ENV{'PWD'} = Win32::GetCwd();
309 $ENV{'PWD'} =~ s:\\:/:g ;
313 *_NT_cwd = \&_win32_cwd if (!defined &_NT_cwd &&
314 defined &Win32::GetCwd);
316 *_NT_cwd = \&_os2_cwd unless defined &_NT_cwd;
319 if (!defined &Dos::GetCwd) {
320 $ENV{'PWD'} = `command /c cd`;
322 $ENV{'PWD'} =~ s:\\:/:g ;
324 $ENV{'PWD'} = Dos::GetCwd();
330 $ENV{'PWD'} = `/usr/bin/fullpath -t`;
336 my $path = shift || '.';
337 my $realpath=`/usr/bin/fullpath -t $path`;
343 no warnings; # assignments trigger 'subroutine redefined' warning
347 *getcwd = \&_vms_cwd;
348 *fastcwd = \&_vms_cwd;
349 *fastgetcwd = \&_vms_cwd;
350 *abs_path = \&_vms_abs_path;
351 *fast_abs_path = \&_vms_abs_path;
353 elsif ($^O eq 'NT' or $^O eq 'MSWin32') {
354 # We assume that &_NT_cwd is defined as an XSUB or in the core.
357 *fastcwd = \&_NT_cwd;
358 *fastgetcwd = \&_NT_cwd;
359 *abs_path = \&fast_abs_path;
361 elsif ($^O eq 'os2') {
362 # sys_cwd may keep the builtin command
363 *cwd = defined &sys_cwd ? \&sys_cwd : \&_os2_cwd;
367 *abs_path = \&fast_abs_path;
369 elsif ($^O eq 'dos') {
371 *getcwd = \&_dos_cwd;
372 *fastgetcwd = \&_dos_cwd;
373 *fastcwd = \&_dos_cwd;
374 *abs_path = \&fast_abs_path;
376 elsif ($^O eq 'qnx') {
378 *getcwd = \&_qnx_cwd;
379 *fastgetcwd = \&_qnx_cwd;
380 *fastcwd = \&_qnx_cwd;
381 *abs_path = \&_qnx_abs_path;
382 *fast_abs_path = \&_qnx_abs_path;
384 elsif ($^O eq 'cygwin') {
388 *abs_path = \&fast_abs_path;
392 # package main; eval join('',<DATA>) || die $@; # quick test
397 BEGIN { import Cwd qw(:DEFAULT chdir); }
398 print join("\n", cwd, getcwd, fastcwd, "");
400 print join("\n", cwd, getcwd, fastcwd, "");