source: trunk/essentials/dev-lang/perl/lib/pwd.pl

;# pwd.pl - keeps track of current working directory in PWD environment var
;#
#
# This library is no longer being maintained, and is included for backward
# compatibility with Perl 4 programs which may require it.
#
# In particular, this should not be used as an example of modern Perl
# programming techniques.
#
# Suggested alternative: Cwd
#
;# $RCSfile: pwd.pl,v $$Revision: 4.1 $$Date: 92/08/07 18:24:11 $
;#
;# $Log:        pwd.pl,v $
;#
;# Usage:
;#      require "pwd.pl";
;#      &initpwd;
;#      ...
;#      &chdir($newdir);

package pwd;

sub main'initpwd {
    if ($ENV{'PWD'}) {
        local($dd,$di) = stat('.');
        local($pd,$pi) = stat($ENV{'PWD'});
        if (!defined $dd or !defined $pd or $di != $pi or $dd != $pd) {
            chop($ENV{'PWD'} = `pwd`);
        }
    }
    else {
        chop($ENV{'PWD'} = `pwd`);
    }
    if ($ENV{'PWD'} =~ m|(/[^/]+(/[^/]+/[^/]+))(.*)|) {
        local($pd,$pi) = stat($2);
        local($dd,$di) = stat($1);
        if (defined $pd and defined $dd and $di == $pi and $dd == $pd) {
            $ENV{'PWD'}="$2$3";
        }
    }
}

sub main'chdir {
    local($newdir) = shift;
    $newdir =~ s|/{2,}|/|g;
    if (chdir $newdir) {
        if ($newdir =~ m#^/#) {
            $ENV{'PWD'} = $newdir;
        }
        else {
            local(@curdir) = split(m#/#,$ENV{'PWD'});
            @curdir = '' unless @curdir;
            foreach $component (split(m#/#, $newdir)) {
                next if $component eq '.';
                pop(@curdir),next if $component eq '..';
                push(@curdir,$component);
            }
            $ENV{'PWD'} = join('/',@curdir) || '/';
        }
    }
    else {
        0;
    }
}

1;