What script is this, and where is it? (Re: who am I?)

I avoid FindBin since the it has problems. There are easy to use alternatives:

Script's Path
(Fully Qualified)

use Cwd qw( realpath );
$script_fqn = realpath($0);
[download]

Script's Name

use File::Basename qw( basename );
$script_fn = basename($0);
[download]

Script's Dir
(Fully Qualified)

use Cwd            qw( realpath );
use File::Basename qw( dirname );
$script_dir_fqn = dirname(realpath($0));
[download]

Update: I originally use File::Spec::Functions's rel2abs, but it doesn't handle symlinks properly. I've updated the table to use Cwd's realpath which does, as per replies.

Comment on What script is this, and where is it? (Re: who am I?) Select or Download Code

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Re: What script is this, and where is it? (Re: who am I?) by AZed (Monk) on Sep 24, 2008 at 22:21 UTC
All of those mechanisms break if the script is being called by a symlink, and particularly so if nested symlinks are involved. You need to `readlink($0) if (-l $0)` first, and then check, and even then, it won't give you the same output as FindBin::RealBin. Create the following directory structure in /var/tmp. Set up directories as follows (you'll need root for /usr/local/bin, so feel free to make the last step anywhere else in your path that you'd like): `cd /var/tmp mkdir mydir mkdir datadir mkdir otherdir cd otherdir ln -s ../mydir symdir` [download] Now take the following code and put it in /var/tmp/mydir/myname.pl: #!/usr/bin/perl use strict; use warnings; use FindBin; use File::Basename qw( dirname ); use File::Spec::Functions qw( rel2abs ); my $name = $0; $name = readlink($name) if(-l $name); print "Finding a data path:\n\n"; print 'dirname($name):',dirname($name),"/../datadir\n"; print 'dirname(rel2abs($name)):',dirname(rel2abs($name)),"/../datadir\ +n"; print 'dirname($0):',dirname($0),"/../datadir\n"; print 'dirname(rel2abs($0)):',dirname(rel2abs($0)),"/../datadir\n"; print '$FindBin::RealBin:',$FindBin::RealBin,"/../datadir\n"; [download] Symlink /var/tmp/symdir/myname.pl to /usr/local/bin/myname (or somewhere else on your path, if you can't or don't want to tamper with a system directory). Run 'myname'. You get: `Finding a data path: dirname($name):/var/tmp/otherdir/symdir/../datadir dirname(rel2abs($name)):/var/tmp/otherdir/symdir/../datadir dirname($0):/usr/local/bin/../datadir dirname(rel2abs($0)):/usr/local/bin/../datadir $FindBin::RealBin:/var/tmp/mydir/../datadir` [download] Only FindBin correctly points you to the correct data directory location. Frankly, even without symlink forests, FindBin is more readable, though.	[reply] [d/l] [select]
Re^2: What script is this, and where is it? (Re: who am I?) by ikegami (Patriarch) on Sep 24, 2008 at 22:45 UTC
All of those mechanisms break if the script is being called by a symlink, and particularly so if nested symlinks are involved. You need to readlink($0) if (-l $0) first, Agreed. Only FindBin correctly points you to the correct data directory location. That's wrong. `/var/tmp/otherdir/symdir/../datadir` [download] is the same directory as `/var/tmp/mydir/../datadir` [download] so you demonstrated that working with readlinked `$0` works. even then, it won't give you the same output as FindBin::RealBin. Doesn't matter. FindBin is more readable, though. What good is readable if it doesn't work as well. And I don't see how `dirname($script_qn)` is less readable than `$FindBin::RealBin`.	[reply] [d/l] [select]
Re^3: What script is this, and where is it? (Re: who am I?) by AZed (Monk) on Sep 24, 2008 at 22:49 UTC
Edit: claims withdrawn. See below. Original message preserved below the jump. Read more... (2 kB)	[reply] [d/l] [select]
Re^4: What script is this, and where is it? (Re: who am I?) by ikegami (Patriarch) on Sep 24, 2008 at 23:10 UTC
Re^5: What script is this, and where is it? (Re: who am I?) by massa (Hermit) on Sep 25, 2008 at 00:26 UTC
Some notes below your chosen depth have not been shown here
Re^5: What script is this, and where is it? (Re: who am I?) by AZed (Monk) on Sep 25, 2008 at 00:53 UTC
Some notes below your chosen depth have not been shown here
Re: What script is this, and where is it? (Re: who am I?) by Anonymous Monk on Sep 25, 2008 at 06:45 UTC
rel2abs doesn't have a problem with symlinks as No checks against the filesystem are made. , it simply uses Cwd::cwd() as the base (rel2abs($path,$base)).	[reply]
Re^2: What script is this, and where is it? (Re: who am I?) by ikegami (Patriarch) on Sep 25, 2008 at 06:52 UTC
That it doesn't check against the file system is the problem. The goal is to find a file or directory relative to the placement of the script, not relative to the placement of a shortcut to the script.	[reply]