How do I get the full path to a Perl script that is executing?

Question

There are a few ways:

• $0 is the currently executing script as provided by POSIX, relative to the current working directory if the script is at or below the CWD
• Additionally, cwd(), getcwd() and abs_path() are provided by the Cwd module and tell you where the script is being run from
• The module FindBin provides the $Bin & $RealBin variables that usually are the path to the executing script; this module also provides $Script & $RealScript that are the name of the script
• __FILE__ is the actual file that the Perl interpreter deals with during compilation, including its full path.

I've seen the first three ($0, the Cwd module and the FindBin module) fail under mod_perl spectacularly, producing worthless output such as '.' or an empty string. In such environments, I use __FILE__ and get the path from that using the File::Basename module:

use File::Basename;
my $dirname = dirname(__FILE__);

$0 is typically the name of your program, so how about this?

use Cwd 'abs_path';
print abs_path($0);

Seems to me that this should work as abs_path knows if you are using a relative or absolute path.

Update For anyone reading this years later, you should read Drew's answer. It's much better than mine.

use File::Spec;
File::Spec->rel2abs( __FILE__ );

http://perldoc.perl.org/File/Spec/Unix.html

I think the module you're looking for is FindBin:

#!/usr/bin/perl
use FindBin;

$0 = "stealth";
print "The actual path to this is: $FindBin::Bin/$FindBin::Script\n";

You could use FindBin, Cwd, File::Basename, or a combination of them. They're all in the base distribution of Perl IIRC.

I used Cwd in the past:

Cwd:

use Cwd qw(abs_path);
my $path = abs_path($0);
print "$path\n";

Getting the absolute path to $0 or __FILE__ is what you want. The only trouble is if someone did a chdir() and the $0 was relative -- then you need to get the absolute path in a BEGIN{} to prevent any surprises.

FindBin tries to go one better and grovel around in the $PATH for something matching the basename($0), but there are times when that does far-too-surprising things (specifically: when the file is "right in front of you" in the cwd.)

File::Fu has File::Fu->program_name and File::Fu->program_dir for this.