http://qs321.pair.com?node_id=11145863

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

Esteemed Monks,

I am trying to translate the following Node.js fragment to Perl (it takes a URL and sort of chdir to it, clever enough to remove endpoint if a file and query):

const url = require('url');
const x = 'http:/a.com/a/b/c/d/e.json?x=1&y=2';
const y = '../../../';
console.log(url.resolve(x, y));

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result is : http:/a.com/a/

Now, if x='http:/a.com/a/b/c/d/e.json/?x=1&y=2'; (i.e. the path points to a "directory" rather than to a "file") the result is http:/a.com/a/b/ (as expected IMO)

I tried to do this with URI but failed:

use URI;
my $x = 'http:/a.com/a/b/c/d/e.json?x=1&y=2';
my $y = '../../../';
my $u = URI->new($x);
my $p = $u->path().'/'.$y;
$u->path($p);
print $u;
<c>
<p>With this result: <c>http:/a.com/a/b/c/d/e.json/../../../?x=1&y=2

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The Node.js version seems to be able to understand that the last segment before the query is a "file" and removes it. Then it does the merging of the two paths including successful relative operations (../). What is the safest way to achieve that behaviour in Perl? The last resort would be to shell-out to Node.js ...

bw, bliako

Replies are listed 'Best First'.
Re: URL resolve (operations on path etc.)
by haukex (Archbishop) on Jul 31, 2022 at 07:52 UTC 
    use warnings;
use strict;
use URI;

my $x = 'http://a.com/a/b/c/d/e.json?x=1&y=2';
my $y = '../../../';
my $u = URI->new($y);
print $u->abs($x), "\n";

__END__

http://a.com/a/

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      Thanks haukex++ (I swear last night abs was not working!!!!!!)

      EDIT!: ouchhhh I was doing the reverse!!!!!:

      # this is wrong, note new($x)!! abs($y) it should be the reverse
my $u = URI->new($x); # this is wrong
print $u->abs($y), "\n"; # this is wrong

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      Edit2: that's definetely an X-Y problem hehe

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      Could this be resolved with a regex maybe? Like for example: 

      #!/usr/bin/perl

use strict;
use warnings;

my $PATH = 'http://a.com/a/b/c/d/e.json?something' . '/' . '/../../../
+';
$PATH =~ tr|/||s;
my $PREV = 0;
my $LEN;
for (;;)
{
  $PATH =~ s/\/[^\/]+\/\.\.//;
  $LEN = length($PATH);
  last if ($PREV == $LEN);
  $PREV = $LEN;
}
print $PATH;

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      I put the regex in a for(;;) loop, because adding global flag didn't do what I want:

      $PATH =~ s/\/[^\/]+\/\.\.//g;

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Re: URL resolve (operations on path etc.)
by Your Mother (Archbishop) on Jul 31, 2022 at 17:27 UTC

    haukex already solved it but this is the way I generally handle these. It lends itself to bulk changes; URI.

    ~>perl -MURI -E '$x = "http://a.com/a/b/c/d/e.json?x=1&y=2"; $y = "../
+../../"; say URI->new_abs($y,$x);'
http://a.com/a/

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