How do I change .. to the real filename?

dcardamo has asked for the wisdom of the Perl Monks concerning the following question: ⭐ (regular expressions)

Replies are listed 'Best First'.
Re: How do I change .. to the real filename?⭐ by merlyn (Sage) on Jan 22, 2001 at 08:13 UTC
`use File::Spec; print File::Spec->rel2abs("/home/projects/..");` [download]	[reply] [d/l]
Re: How do I change .. to the real filename? by AltBlue (Chaplain) on Jan 27, 2001 at 03:01 UTC
`use Cwd 'abs_path'; print abs_path('/home/projects/..');` [download]	[reply] [d/l]
Re: How do I change .. to the real filename? by matthewm (Initiate) on Jan 25, 2001 at 21:01 UTC
To answer your specifc example.. `$file =~ s%/[^/]+/\.\.$%%` [download] ... will eat the last directory name that's up'ed by the trailing .. To give a more general/complete example that can handle multiple .'s and ..'s at any point in the path. `# colapse /./ and /.$ 1 while ($file =~ s%/\.(/\|$)%$1%g); # colapse /dir/../ and /dir/..$ # ignore /../../ and /../..$ 1 while ($file =~ s%/[^/]+/(?<!/\.\./)\.\.(/\|$)%$1%g); # remove ^dir/../ and ^dir/../ # ignore ^../../ and ^../.. 1 while ($file =~ s%^[^/]+/(?<!^\.\./)\.\.(/\|$)%%); # colapse ^/../ to / 1 while ($file =~ s%^/\.\./%/%); # expand null to . $file =~ s%^$%.%;` [download] We need the itterations of each loop as each substitution may reveal additional matchs. We need multiple expressions to get the order of susbistion right. That is /../../ should colapse the two proceding directoires and not itself. I'm sure it can be reduced more than that but it is as simple as I can see it can be and still catch all the special cases. I use something very similar to this at the beginning of my scripts to get the conical path for $0 and not the called path. Although spliting the path into its components and working backwards is probably easier/clearer than using a regex.	[reply] [d/l] [select]
Re: How do I change .. to the real filename? by dcardamo (Initiate) on Jan 23, 2001 at 02:30 UTC
I tried the first solution, and it didn't work properly. I haven't tried the second, but here is a non-regex routine that I wrote to do that: `sub relpath($) { my $file = shift; my $newfile = ""; $file =~ s/\n//g; # remove new lines my @peices = split /\//, $file; for (my $i = 0; $i <= $#peices; $i++) { if ($peices[$i + 1] eq "..") { last; } if ($peices[$i] ne ".") { $newfile .= "/$peices[$i]"; } } $newfile =~ s/\/\//\//g; return $newfile; }` [download]	[reply] [d/l]
Re: How do I change .. to the real filename? by Shakya (Initiate) on Oct 06, 2007 at 18:59 UTC
You can even try this - `1 while ($string =~ s!(/(?:[^/.]+/))((?:[^/.]+/)+\.\./?)(.)$!$1$3!g) +;` [download]	[reply] [d/l]
Re: How do I change .. to the real filename? by Gloom (Monk) on Jan 22, 2001 at 22:45 UTC
Or maybe something like this ? `$filename =~ s/\/\w+\/\.\.//g;` [download] Originally posted as a Categorized Answer.	[reply] [d/l]