File::Spec is the long-awaited standard method for doing common tasks with file names and paths (file specifications or file specs) in a way that is portable between different operating systems.

The Good

What it can do:

• $cpath = File::Spec->canonpath( $path );
• $dirpath = File::Spec->catdir( $dir1, $dir2, $dir3 );
• $filepath = File::Spec->catfile( $dir1, $dir2, $dir3, $file );
• $curdir= File::Spec->curdir();  # "." on Unix
• $nul= File::Spec->devnull();    # "/dev/null" on Unix
• $root= File::Spec->rootdir();   # "/" on Unix
• $tmpdir= File::Spec->tmpdir();  # "/tmp" or $ENV{TMPDIR}, etc.
• $updir= File::Spec->updir();    # ".." on Unix
• @list= File::Spec->no_upwards( @list ); # Strips "." and ".."
• $ignore= File::Spec->case_tolerant();      # Returns false under Unix
• $abs= File::Spec->file_name_is_absolute($path);
• @path= File::Spec->path();      # Returns $ENV{PATH} as an array.
• ($volume,$dirs,$file)= File::Spec->splitpath( $path [, $no_file ] );
• @dirs= File::Spec->splitdir( $dirs );
• $path= File::Spec->catpath( $vol, $dirs, $file );
• $relpath= File::Spec->abs2rel( $path [, $base ] );
• $abspath= File::Spec->rel2abs( $path [, $base ] );

The Bad

The documentation isn't OS-independent so you have to read the documentation for each OS-specific component of File::Spec. Start with perldoc File::Spec then perldoc File::Spec::Unix (since that part of the module is the most complete).

Not all methods are available on all platforms.

This module isn't available for even slightly old versions of Perl. Until and unless that changes, you may want to back-port the functionality to older versions of Perl yourself so that your code will still port to different OSes.

The Ugly

Getting File::Spec functionality for old versions of Perl in a portable, robust manner. I hope to add more details on this later.