working with relative paths

apotheon has asked for the wisdom of the Perl Monks concerning the following question:

I'm running Perl 5.x on a Debian GNU/Linux system here, and wrote a simple script last night to normalize hundreds of filenames for me. A minor issue I've run into is with defining a directory path for the script to use. A snippet of relevant example code follows (slightly modified so that it makes sense without the rest of the script):

my $direct;
chomp($direct = $ARGV[0]);
chdir($direct);
[download]

Basically, this script as currently written forces me to use absolute paths, whereas I'd like to make it use relative paths. Best would be path relative to where I am in the filesystem when I run it, but it won't even recognize relative path from the location of the script, which just boggles my mind. What am I missing?

I've done searches at PerlMonks, looked through several books (including Visual Quickstart: Perl and CGI for the World Wide Web, the llama, and Perl in a Nutshell), and browsed through online tutorials, but haven't discovered anything particularly helpful on the matter.

- apotheon
CopyWrite Chad Perrin

Comment on working with relative paths Download Code

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Re: working with relative paths by steves (Curate) on Oct 30, 2004 at 01:57 UTC
Relative paths should work with chdir, being relative to where you are when you run (not where the script is). Example from a Solaris Perl 5.8 system: `use strict; use Cwd; print "cwd [1] = ", cwd(), "\n"; chdir("/tmp"); print "cwd [2] = ", cwd(), "\n"; chdir("steve"); # relative! print "cwd [3] = ", cwd(), "\n";` [download] produces: `cwd [1] = /export/home/foo cwd [2] = /tmp cwd [3] = /tmp/steve` [download]	[reply] [d/l] [select]
Re^2: working with relative paths by apotheon (Deacon) on Oct 30, 2004 at 02:19 UTC
Maybe it "should" work (at least I think so), but the problem is that it doesn't. I'm beginning to wonder if it's some kind of system configuration issue. Is there any reason `chdir()` would work differently for a scalar variable than for hardcoded paths? Obviously, I'm trying to make a script that works for more than one filepath without having to rewrite the script every time. - apotheon CopyWrite Chad Perrin	[reply] [d/l]
Re^3: working with relative paths by itub (Priest) on Oct 30, 2004 at 02:29 UTC
chdir has to work or I'll eat my hat, ;-) as it is one of the most fundamental functions. Perhaps if you posted a short but complete example, along with its actual output and the expected result, it would be easier to figure out what's going on. A couple of tricks that might help: use strict, warnings, and diagnostics; try `chdir $direct or die $!` to see if there is an error message.	[reply] [d/l]
Re^4: working with relative paths by apotheon (Deacon) on Oct 30, 2004 at 03:12 UTC
Re^5: working with relative paths by fglock (Vicar) on Oct 30, 2004 at 03:27 UTC
Some notes below your chosen depth have not been shown here
Re: working with relative paths by bobf (Monsignor) on Oct 30, 2004 at 04:00 UTC
Take a look at File::Spec. It has quite a few very handy methods to portably manipulate paths, including `abs2rel` and `rel2abs`, which convert absolute paths to relative paths and visa versa. Unless I'm misunderstanding the problem, you should be able to use them to do what you need (it makes use of `cwd` if a base path is not supplied). HTH	[reply] [d/l] [select]
Re^2: working with relative paths by apotheon (Deacon) on Oct 30, 2004 at 04:07 UTC
It turns out I just made a stupid, boneheaded error, actually, as fglock pointed out above. It looks like File::Spec will be of great use to me in the future, though. Thanks for the link. - apotheon CopyWrite Chad Perrin	[reply]
Re: working with relative paths by TedPride (Priest) on Oct 30, 2004 at 02:33 UTC
Take a look at the following %ENV variables: SCRIPT_NAME : /cgi-local/env.pl DOCUMENT_ROOT : /u/web/folder SCRIPT_FILENAME : /u/web/folder/cgi-bin/env.pl You can use these to start your absolute path, rather than having to enter it by hand, and all you have to do from there is keep track of the current folder with a little creative programming.	[reply]
Re^2: working with relative paths by apotheon (Deacon) on Oct 30, 2004 at 03:05 UTC
This isn't for a website, and I'm not using a cgi-bin. In fact, I don't have any kind of web server installed on this system. I'm just writing Perl on it for system administration tasks, mostly. - apotheon CopyWrite Chad Perrin	[reply]
Re: working with relative paths by ccn (Vicar) on Oct 30, 2004 at 20:05 UTC
Does this help? `use vars qw($Bin $Script); BEGIN { ($Bin, $Script) = split /([^\/\\]+)$/, $0 } chdir $Bin . $ARGV[0];` [download]	[reply] [d/l]
Re^2: working with relative paths by apotheon (Deacon) on Oct 30, 2004 at 20:28 UTC
Changing the way I used `opendir()` helped, actually. See above discussion for details. - apotheon CopyWrite Chad Perrin	[reply] [d/l]
Re^2: working with relative paths by chanio (Priest) on Oct 31, 2004 at 03:55 UTC
`use vars qw($Bin); BEGIN { $Bin = qx(pwd) } chdir $Bin . $ARGV[0];` [download] .{\('v')/} _`(___)' __________________________ Wherever I lay my KNOPPIX disk, a new FREE LINUX nation could be established.	[reply] [d/l]