/ 
File-chdir-0.05
River stage four • 203 direct dependents • 2906 total dependents
/ File::chdir

NAME

File::chdir - a more sensible way to change directories

SYNOPSIS

use File::chdir;
use Cwd;

$CWD = "/foo/bar";     # now in /foo/bar
{
    local $CWD = "/moo/baz";  # now in /moo/baz
    ...
}

# still in /foo/bar!

DESCRIPTION

Perl's chdir() has the unfortunate problem of being very, very, very global. If any part of your program calls chdir() or if any library you use calls chdir(), it changes the current working directory for the whole program.

This sucks.

File::chdir gives you an alternative, $CWD and @CWD. These two variables combine all the power of chdir(), File::Spec and Cwd.

$CWD

Use the $CWD variable instead of chdir() and Cwd.

use File::chdir;
$CWD = $dir;  # just like chdir($dir)!
print $CWD;   # prints the current working directory

It can be localized, and it does the right thing.

$CWD = "/foo";      # it's /foo out here.
{
    local $CWD = "/bar";  # /bar in here
}
# still /foo out here!

$CWD always returns the absolute path.

$CWD and normal chdir() work together just fine.

@CWD

@CWD represents the current working directory as an array, each directory in the path is an element of the array. This can often make the directory easier to manipulate, and you don't have to fumble with File::Spec->splitpath and File::Spec->catdir to make portable code.

# Similar to chdir("/usr/local/src/perl")
@CWD = qw(usr local src perl);

pop, push, shift, unshift and splice all work. pop and push are probably the most useful.

pop @CWD;                 # same as chdir(File::Spec->updir)
push @CWD, 'some_dir'     # same as chdir('some_dir')

@CWD and $CWD both work fine together.

NOTE Due to a perl bug you can't localize @CWD. See "BUGS and CAVEATS" for a work around.

EXAMPLES

(We omit the use File::chdir from these examples for terseness)

Here's $CWD instead of chdir:

$CWD = 'foo';           # chdir('foo')

and now instead of Cwd.

print $CWD;             # use Cwd;  print Cwd::abs_path

you can even do zsh style cd foo bar

$CWD = '/usr/local/foo';
$CWD =~ s/usr/var/;

if you want to localize that, make sure you get the parens right

{
    (local $CWD) =~ s/usr/var/;
    ...
}

It's most useful for writing polite subroutines which don't leave the program in some strange directory:

sub foo {
    local $CWD = 'some/other/dir';
    ...do your work...
}

which is much simplier than the equivalent:

sub foo {
    use Cwd;
    my $orig_dir = Cwd::abs_path;
    chdir('some/other/dir');

    ...do your work...

    chdir($orig_dir);
}

@CWD comes in handy when you want to start moving up and down the directory hierarchy in a cross-platform manner without having to use File::Spec.

pop @CWD;                   # chdir(File::Spec->updir);
push @CWD, 'some', 'dir'    # chdir(File::Spec->catdir(qw(some dir)));

You can easily change your parent directory:

# chdir from /some/dir/bar/moo to /some/dir/foo/moo
$CWD[-2] = 'foo';

BUGS and CAVEATS

local @CWD will not localize @CWD. This is a bug in Perl, you can't localize tied arrays. As a work around localizing $CWD will effectively localize @CWD.

{
    local $CWD;
    pop @CWD;
    ...
}

SEE ALSO

Michael G Schwern <schwern@pobox.com>

HISTORY

I wanted local chdir to work. p5p didn't. Did I let that stop me? No! Did we give up after the Germans bombed Pearl Harbor? Hell, no!

Abigail and/or Bryan Warnock suggested the $CWD thing, I forget which. They were right.

The chdir() override was eliminated in 0.04.