OpenStep 4.2J (Developer)/os42jdev.iso/NextDeveloper/Source/GNU/perl/Perl/lib/Cwd.pm

Perl POD Document | 1995-05-25 | 4.5 KB | 210 lines

package Cwd;
require 5.000;
require Exporter;
use Config;

=head1 NAME

getcwd - get pathname of current working directory

=head1 SYNOPSIS

    require Cwd;
    $dir = Cwd::getcwd();

    use Cwd;
    $dir = getcwd();

    use Cwd 'chdir';
    chdir "/tmp";
    print $ENV{'PWD'};

=head1 DESCRIPTION

The getcwd() function re-implements the getcwd(3) (or getwd(3)) functions
in Perl.  If you ask to override your chdir() built-in function, then your
PWD environment variable will be kept up to date.  (See
L<perlsub/Overriding builtin functions>.)

The fastgetcwd() function looks the same as getcwd(), but runs faster.
It's also more dangerous because you might conceivably chdir() out of a
directory that you can't chdir() back into.

=cut

@ISA = qw(Exporter);
@EXPORT = qw(getcwd fastcwd);
@EXPORT_OK = qw(chdir);


# VMS: $ENV{'DEFAULT'} points to default directory at all times
# 08-Dec-1994  Charles Bailey  [e-mail]
# Note: Use of Cwd::getcwd() or Cwd::chdir() (but not Cwd::fastcwd())
#   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.

# By Brandon S. Allbery
#
# Usage: $cwd = getcwd();

sub getcwd
{
    if($Config{'osname'} eq 'VMS') { return $ENV{'PWD'} = $ENV{'DEFAULT'} }

    my($dotdots, $cwd, @pst, @cst, $dir, @tst);

    unless (@cst = stat('.'))
    {
    warn "stat(.): $!";
    return '';
    }
    $cwd = '';
    $dotdots = '';
    do
    {
    $dotdots .= '/' if $dotdots;
    $dotdots .= '..';
    @pst = @cst;
    unless (opendir(PARENT, $dotdots))
    {
        warn "opendir($dotdots): $!";
        return '';
    }
    unless (@cst = stat($dotdots))
    {
        warn "stat($dotdots): $!";
        closedir(PARENT);
        return '';
    }
    if ($pst[0] == $cst[0] && $pst[1] == $cst[1])
    {
        $dir = '';
    }
    else
    {
        do
        {
        unless (defined ($dir = readdir(PARENT)))
            {
            warn "readdir($dotdots): $!";
            closedir(PARENT);
            return '';
        }
        unless (@tst = lstat("$dotdots/$dir"))
        {
            warn "lstat($dotdots/$dir): $!";
            closedir(PARENT);
            return '';
        }
        }
        while ($dir eq '.' || $dir eq '..' || $tst[0] != $pst[0] ||
           $tst[1] != $pst[1]);
    }
    $cwd = "$dir/$cwd";
    closedir(PARENT);
    } while ($dir);
    chop($cwd); # drop the trailing /
    $cwd;
}



# 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 {
    if($Config{'osname'} eq 'VMS') { return $ENV{'DEFAULT'} }

    my($odev, $oino, $cdev, $cino, $tdev, $tino);
    my(@path, $path);
    local(*DIR);

    ($cdev, $cino) = stat('.');
    for (;;) {
    my $direntry;
    ($odev, $oino) = ($cdev, $cino);
    chdir('..');
    ($cdev, $cino) = stat('.');
    last if $odev == $cdev && $oino == $cino;
    opendir(DIR, '.');
    for (;;) {
        $direntry = readdir(DIR);
        next if $direntry eq '.';
        next if $direntry eq '..';

        last unless defined $direntry;
        ($tdev, $tino) = lstat($direntry);
        last unless $tdev != $odev || $tino != $oino;
    }
    closedir(DIR);
    unshift(@path, $direntry);
    }
    chdir($path = '/' . join('/', @path));
    $path;
}


# keeps track of current working directory in PWD environment var
#
# $RCSfile: pwd.pl,v $$Revision: 4.1 $$Date: 92/08/07 18:24:11 $
#
# $Log:    pwd.pl,v $
#
# Usage:
#    use Cwd 'chdir';
#    chdir $newdir;

$chdir_init = 0;

sub chdir_init{
    if ($ENV{'PWD'}) {
    my($dd,$di) = stat('.');
    my($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|(/[^/]+(/[^/]+/[^/]+))(.*)|) {
    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;
    $newdir =~ s|/{2,}|/|g;
    chdir_init() unless $chdir_init;
    return 0 unless (CORE::chdir $newdir);
    if ($Config{'osname'} eq 'VMS') { return $ENV{PWD} = $ENV{DEFAULT} }

    if ($newdir =~ m#^/#) {
    $ENV{'PWD'} = $newdir;
    }else{
    my(@curdir) = split(m#/#,$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) || '/';
    }
}

1;