unreal absolute path

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

I am writing a tool that works like a directory list (ls, dir, etc) and I'd like to report something akin to the absolute path for each of the files. However, I don't want to see mountpoint information and I don't want symlinks resolved.

IE:
According to the file system, my working dir is here:
/base/path/to/a/
if I do a directory listing, I see:
file.txt

If you use the cwd module and check the abs_path of the file, you get
/mountpoint/base/path/linked/to/a/file.txt

(/base is a mountpoint; plus there is a symlink here /base/path/to -> /base/path/linked/to)

Now, of course, I may not actually be inside the directory that I'd like to work with; I might want to call this from "/base", with "path/to/a" as an argument. Can anyone suggest a way for me to report the "unreal" absolute path that would look like this?
/some/base/path/to/a/file.txt

Thanks.

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Re: unreal absolute path by zentara (Cardinal) on Nov 28, 2004 at 12:31 UTC
Without wracking my brain too hard, I think you are looking for File::Spec `#!/usr/bin/perl use File::Spec; my $abs_path = File::Spec->rel2abs( $rel_path ); my $rel_path = File::Spec->abs2rel( $path, $base );` [download] I'm not really a human, but I play one on earth. flash japh	[reply] [d/l]
Re: unreal absolute path by gaal (Parson) on Nov 28, 2004 at 08:26 UTC
If there are several different ways to get to your path, how would you choose which to use? Your shell has that information because it keeps track of where you `cd`'ed to; but it doesn't communitacate that to anyone else. (If you're in `/a`, and have symlink `b -> /c`, and type in `cd b ; cd ..` -- where do you end up? Different shells do different things here.)	[reply] [d/l] [select]
Re: unreal absolute path by ikegami (Patriarch) on Nov 28, 2004 at 07:29 UTC
Is there anything wrong with `my $dir_name = '/base/path/to/a/'; my $dh = DirHandle->new($dir_name) or die("booooo $!\n"); my $file_name; while (defined($file_name = $dh->read())) { my $full_file_name = "$dir_name/$file_name"; ... }` [download]	[reply] [d/l]
Re^2: unreal absolute path by kgimpel (Acolyte) on Nov 28, 2004 at 07:46 UTC
Not to be obtuse about it, but my whole problem is generating the info for the first line in your solution. Now that I consider it, this may be more of a unix question than a perl one. If I run the script from inside a given directory, how do I determine where that dir is located? My unix prompt reports the info in the way I'd like to collect it for the script, but it has already travaeresed symlinks to get there. Perhaps I should be asking for something other than the current working dir?	[reply]
Re^3: unreal absolute path by ikegami (Patriarch) on Nov 28, 2004 at 08:11 UTC
Sorry for misunderstanding. I tried a few things... $ \ls -ldF /home2/ikegami lrwxr-xr-x ... /home2/ikegami@ -> /home3/ikegami $ \ls -ldF /home3/ikegami drwx--x--x ... /home3/ikegami/ $ pwd /home2/ikegami $ perl -e 'print `pwd`' /home3/ikegami $ perl -e 'print `pwd -L`' /home2/ikegami $ perl -e 'chdir "www"; print `pwd -L`' /home3/ikegami/www $ perl -le 'use Cwd; print cwd;' /home3/ikegami $ perl -le 'use Cwd; print getcwd;' /home3/ikegami $ echo $PWD /home2/ikegami $ perl -le 'print $ENV{"PWD"};' /home2/ikegami $ perl -le 'chdir("www"); print $ENV{"PWD"};' /home2/ikegami $ perl -le 'use Cwd qw( chdir ); chdir("www"); print $ENV{"PWD"};' /home2/ikegami/www [download] `pwd -L` seems to work, at the cost of creating a child process and running `pwd`. It stops working if `chdir` is used, unfortunately. If the calling shell provides `$ENV{"PWD"}`, you save the spawning cost. Of course, it doesn't change if `chdir` is used. ... unless you use the `chdir` from `Cwd` everywhere.	[reply] [d/l] [select]
Re: unreal absolute path by ysth (Canon) on Nov 28, 2004 at 10:29 UTC
Can't you just construct the name the way you looked it up? So if you are in /base, and you got file.txt in a directory listing of path/to/a/, your path is /base/path/to/a/file.txt. If you are wanting to use the actual path used to set the current directory to /base, you might want to check $PWD instead of cwd().	[reply]