6 Cwd - get pathname of current working directory
14 my $abs_path = abs_path($file);
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.
22 By default, it exports the functions cwd(), getcwd(), fastcwd(), and
23 fastgetcwd() into the caller's namespace.
26 =head2 getcwd and friends
28 Each of these functions are called without arguments and return the
29 absolute path of the current working directory.
37 Returns the current working directory.
39 Re-implements the getcwd(3) (or getwd(3)) functions in Perl.
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
49 Unfortunately, cwd() tends to break if called under taint mode.
55 A more dangerous version of getcwd(), but potentially faster.
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.
68 my $cwd = fastgetcwd();
70 The fastgetcwd() function is provided as a synonym for cwd().
75 =head2 abs_path and friends
77 These functions are exported only on request. They each take a single
78 argument and return the absolute pathname for it.
84 my $abs_path = abs_path($file);
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).
92 my $abs_path = realpath($file);
94 A synonym for abs_path().
98 my $abs_path = abs_path($file);
100 A more dangerous, but potentially faster version of abs_path.
106 If you ask to override your chdir() built-in function,
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
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.
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
144 our $VERSION = '2.06';
146 use base qw/ Exporter /;
147 our @EXPORT = qw(cwd getcwd fastcwd fastgetcwd);
148 our @EXPORT_OK = qw(chdir abs_path fast_abs_path realpath fast_realpath);
150 # sys_cwd may keep the builtin command
152 # All the functionality of this module may provided by builtins,
153 # there is no sense to process the rest of the file.
154 # The best choice may be to have this in BEGIN, but how to return from BEGIN?
156 if ($^O eq 'os2' && defined &sys_cwd && defined &sys_abspath) {
162 *abs_path = \&sys_abspath;
163 *fast_abs_path = \&abs_path;
164 *realpath = \&abs_path;
165 *fast_realpath = \&abs_path;
171 undef *Cwd::fastcwd; # avoid redefinition warning
172 XSLoader::load('Cwd');
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.
180 foreach my $try (qw(/bin/pwd /usr/bin/pwd)) {
188 # The 'natural and safe form' for UNIX (pwd may be setuid root)
190 my $cwd = `$pwd_cmd`;
191 # `pwd` may fail e.g. if the disk is full
192 chomp($cwd) if defined $cwd;
196 # Since some ports may predefine cwd internally (e.g., NT)
197 # we take care not to override an existing definition for cwd().
199 unless(defined &cwd) {
200 # The pwd command is not available in some chroot(2)'ed environments
201 if($^O eq 'MacOS' || grep { -x "$_/pwd" } split(':', $ENV{PATH})) {
202 *cwd = \&_backtick_pwd;
209 # set a reasonable (and very safe) default for fastgetcwd, in case it
210 # isn't redefined later (20001212 rspier)
213 # By Brandon S. Allbery
215 # Usage: $cwd = getcwd();
225 # Usage: $cwd = &fastcwd;
227 # This is a faster version of getcwd. It's also more dangerous because
228 # you might chdir out of a directory that you can't chdir back into.
231 my($odev, $oino, $cdev, $cino, $tdev, $tino);
235 my($orig_cdev, $orig_cino) = stat('.');
236 ($cdev, $cino) = ($orig_cdev, $orig_cino);
239 ($odev, $oino) = ($cdev, $cino);
240 CORE::chdir('..') || return undef;
241 ($cdev, $cino) = stat('.');
242 last if $odev == $cdev && $oino == $cino;
243 opendir(DIR, '.') || return undef;
245 $direntry = readdir(DIR);
246 last unless defined $direntry;
247 next if $direntry eq '.';
248 next if $direntry eq '..';
250 ($tdev, $tino) = lstat($direntry);
251 last unless $tdev != $odev || $tino != $oino;
254 return undef unless defined $direntry; # should never happen
255 unshift(@path, $direntry);
257 $path = '/' . join('/', @path);
258 if ($^O eq 'apollo') { $path = "/".$path; }
259 # At this point $path may be tainted (if tainting) and chdir would fail.
260 # To be more useful we untaint it then check that we landed where we started.
261 $path = $1 if $path =~ /^(.*)\z/s; # untaint
262 CORE::chdir($path) || return undef;
263 ($cdev, $cino) = stat('.');
264 die "Unstable directory path, current directory changed unexpectedly"
265 if $cdev != $orig_cdev || $cino != $orig_cino;
270 # Keeps track of current working directory in PWD environment var
278 if ($ENV{'PWD'} and $^O ne 'os2' and $^O ne 'dos' and $^O ne 'MSWin32') {
279 my($dd,$di) = stat('.');
280 my($pd,$pi) = stat($ENV{'PWD'});
281 if (!defined $dd or !defined $pd or $di != $pi or $dd != $pd) {
287 $wd = Win32::GetFullPathName($wd) if $^O eq 'MSWin32';
290 # Strip an automounter prefix (where /tmp_mnt/foo/bar == /foo/bar)
291 if ($^O ne 'MSWin32' and $ENV{'PWD'} =~ m|(/[^/]+(/[^/]+/[^/]+))(.*)|s) {
292 my($pd,$pi) = stat($2);
293 my($dd,$di) = stat($1);
294 if (defined $pd and defined $dd and $di == $pi and $dd == $pd) {
302 my $newdir = @_ ? shift : ''; # allow for no arg (chdir to HOME dir)
303 $newdir =~ s|///*|/|g unless $^O eq 'MSWin32';
304 chdir_init() unless $chdir_init;
306 if ($^O eq 'MSWin32') {
307 # get the full path name *before* the chdir()
308 $newpwd = Win32::GetFullPathName($newdir);
311 return 0 unless CORE::chdir $newdir;
314 return $ENV{'PWD'} = $ENV{'DEFAULT'}
316 elsif ($^O eq 'MacOS') {
317 return $ENV{'PWD'} = cwd();
319 elsif ($^O eq 'MSWin32') {
320 $ENV{'PWD'} = $newpwd;
324 if ($newdir =~ m#^/#s) {
325 $ENV{'PWD'} = $newdir;
327 my @curdir = split(m#/#,$ENV{'PWD'});
328 @curdir = ('') unless @curdir;
330 foreach $component (split(m#/#, $newdir)) {
331 next if $component eq '.';
332 pop(@curdir),next if $component eq '..';
333 push(@curdir,$component);
335 $ENV{'PWD'} = join('/',@curdir) || '/';
341 # In case the XS version doesn't load.
342 *abs_path = \&_perl_abs_path unless defined &abs_path;
345 my $start = @_ ? shift : '.';
346 my($dotdots, $cwd, @pst, @cst, $dir, @tst);
348 unless (@cst = stat( $start ))
350 carp "stat($start): $!";
359 unless (opendir(PARENT, $dotdots))
361 carp "opendir($dotdots): $!";
364 unless (@cst = stat($dotdots))
366 carp "stat($dotdots): $!";
370 if ($pst[0] == $cst[0] && $pst[1] == $cst[1])
378 unless (defined ($dir = readdir(PARENT)))
380 carp "readdir($dotdots): $!";
384 $tst[0] = $pst[0]+1 unless (@tst = lstat("$dotdots/$dir"))
386 while ($dir eq '.' || $dir eq '..' || $tst[0] != $pst[0] ||
389 $cwd = (defined $dir ? "$dir" : "" ) . "/$cwd" ;
391 } while (defined $dir);
392 chop($cwd) unless $cwd eq '/'; # drop the trailing /
397 # added function alias for those of us more
398 # used to the libc function. --tchrist 27-Jan-00
399 *realpath = \&abs_path;
404 my $path = @_ ? shift : File::Spec->curdir;
405 CORE::chdir($path) || croak "Cannot chdir to $path:$!";
406 my $realpath = getcwd();
407 CORE::chdir($cwd) || croak "Cannot chdir back to $cwd:$!";
411 # added function alias to follow principle of least surprise
412 # based on previous aliasing. --tchrist 27-Jan-00
413 *fast_realpath = \&fast_abs_path;
416 # --- PORTING SECTION ---
418 # VMS: $ENV{'DEFAULT'} points to default directory at all times
419 # 06-Mar-1996 Charles Bailey bailey@newman.upenn.edu
420 # Note: Use of Cwd::chdir() causes the logical name PWD to be defined
421 # in the process logical name table as the default device and directory
422 # seen by Perl. This may not be the same as the default device
423 # and directory seen by DCL after Perl exits, since the effects
424 # the CRTL chdir() function persist only until Perl exits.
427 return $ENV{'DEFAULT'};
431 return $ENV{'DEFAULT'} unless @_;
432 my $path = VMS::Filespec::pathify($_[0]);
433 croak("Invalid path name $_[0]") unless defined $path;
434 return VMS::Filespec::rmsexpand($path);
438 $ENV{'PWD'} = `cmd /c cd`;
444 $ENV{'PWD'} = Win32::GetCwd();
448 *_NT_cwd = \&_win32_cwd if (!defined &_NT_cwd &&
449 defined &Win32::GetCwd);
451 *_NT_cwd = \&_os2_cwd unless defined &_NT_cwd;
454 if (!defined &Dos::GetCwd) {
455 $ENV{'PWD'} = `command /c cd`;
458 $ENV{'PWD'} = Dos::GetCwd();
464 $ENV{'PWD'} = `/usr/bin/fullpath -t`;
470 my $path = @_ ? shift : '.';
471 my $realpath=`/usr/bin/fullpath -t $path`;
477 $ENV{'PWD'} = EPOC::getcwd();
482 no warnings; # assignments trigger 'subroutine redefined' warning
486 *getcwd = \&_vms_cwd;
487 *fastcwd = \&_vms_cwd;
488 *fastgetcwd = \&_vms_cwd;
489 *abs_path = \&_vms_abs_path;
490 *fast_abs_path = \&_vms_abs_path;
492 elsif ($^O eq 'NT' or $^O eq 'MSWin32') {
493 # We assume that &_NT_cwd is defined as an XSUB or in the core.
496 *fastcwd = \&_NT_cwd;
497 *fastgetcwd = \&_NT_cwd;
498 *abs_path = \&fast_abs_path;
499 *realpath = \&fast_abs_path;
501 elsif ($^O eq 'os2') {
502 # sys_cwd may keep the builtin command
503 *cwd = defined &sys_cwd ? \&sys_cwd : \&_os2_cwd;
507 *abs_path = \&fast_abs_path;
509 elsif ($^O eq 'dos') {
511 *getcwd = \&_dos_cwd;
512 *fastgetcwd = \&_dos_cwd;
513 *fastcwd = \&_dos_cwd;
514 *abs_path = \&fast_abs_path;
516 elsif ($^O =~ m/^(?:qnx|nto)$/ ) {
518 *getcwd = \&_qnx_cwd;
519 *fastgetcwd = \&_qnx_cwd;
520 *fastcwd = \&_qnx_cwd;
521 *abs_path = \&_qnx_abs_path;
522 *fast_abs_path = \&_qnx_abs_path;
524 elsif ($^O eq 'cygwin') {
528 *abs_path = \&fast_abs_path;
530 elsif ($^O eq 'epoc') {
532 *getcwd = \&_epoc_cwd;
533 *fastgetcwd = \&_epoc_cwd;
534 *fastcwd = \&_epoc_cwd;
535 *abs_path = \&fast_abs_path;
537 elsif ($^O eq 'MacOS') {
541 *abs_path = \&fast_abs_path;