getcwd - get pathname of current working directory
use Cwd;
$dir = cwd;
use Cwd;
$dir = getcwd;
use Cwd;
$dir = fastgetcwd;
use Cwd 'chdir';
chdir "/tmp";
print $ENV{'PWD'};
use Cwd 'abs_path'; # aka realpath()
print abs_path($ENV{'PWD'});
use Cwd 'fast_abs_path';
print fast_abs_path($ENV{'PWD'});The getcwd() function re-implements the getcwd(3) (or getwd(3)) functions in Perl.
The abs_path() function takes a single argument and returns the absolute pathname for that argument. It uses the same algorithm as getcwd(). (Actually, getcwd() is abs_path(".")) Symbolic links and relative-path components ("." and "..") are resolved to return the canonical pathname, just like realpath(3). Also callable as realpath().
The fastcwd() function looks the same as getcwd(), but runs faster. It's also more dangerous because 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 die with the message "Unstable directory path, current directory changed unexpectedly". That should never happen.
The fast_abs_path() function looks the same as abs_path(), but runs faster. And like fastcwd() is more dangerous.
The cwd() function looks the same as getcwd and fastgetcwd but is implemented using the most natural and safe form for the current architecture. For most systems it is identical to `pwd` (but without the trailing line terminator).
It is recommended that cwd (or another *cwd() function) is used in all code to ensure portability.
If you ask to override your chdir() built-in function, then your PWD environment variable will be kept up to date. (See "Overriding Builtin Functions" in perlsub.) Note that it will only be kept up to date if all packages which use chdir import it from Cwd.