Weird File::Basename::basename

[McA]

Hi Monks,

just stumbled on the following behaviour of File::Basename::basename.

#!/usr/bin/perl
use 5.010;
use strict;
use warnings;

use File::Basename;
say "$File::Basename::VERSION\n";

my $filename = '';
say $filename, ' - basename($filename) -> ', basename($filename);
say $filename, ' - dirname($filename) -> ', dirname($filename);

The basename of an empty string is ./ which I really didn't expect. To cite the documentation:

dirname() and basename() emulate the behaviours, and quirks, of the shell and C functions of the same name. See each function's documentation for details.

But basename of empty string on bash is an empty string. The same for C library basename.

Is this a bug?

McA

[Anonymous Monk]

Is this a bug?

Yes , I think so.

See http://perl5.git.perl.org/perl.git/blob/HEAD:/lib/File/Basename.t, its a typical bug (if a boundary condition isn't tested, chances are it'll be broken)

OTOH, on the scale of importance/severity, I would classify this bug as unimportant

FWIW, you should perlbug it just the same :) functions should do what they claim to do -- and they might as well explicitly spell out what that is instead of merely referring to the manpages -- I'll bet if the pod actually spelled out the full behaviour, there would have been a test for it in the test suite :)

[hdb]

On the importance of this bug: In a way "./" is the neutral element in pathes in the sense of adding it anywhere in the path does not change anything (except in the middle of a name obviously).

One exception springs to mind: When executing a command it does make a difference whether to say

system("somecommand");    # or
system("./somecommand");

Whether or not this can happen due to the usage of basename('') in any practical example I am not sure.

[Anonymous Monk]

When executing a command it does make a difference whether to say "foo" or "./foo"

not on cmd.exe, cwd is first place searched

:) spec/basename are useful, but they're kinda low-level, I prefer abstractions like Path::Class and Badger::Filesystem and absolute paths, so file( ... )->absolute

[RichardK]

I prefer to use File::Spec splitpath, as it seems more logical and does the right thing -- even if volume doesn't make any sense on a proper system ;)

[McA]

Hi,

UPDATE: I made a little test program in C to see the behaviour there. Interestingly the basename('') is '.'. So it seems we have now three different results:

• Shell: basename '' => ''
• File::Basename: basename '' => './'
• C basename: basename '' => '.'

McA