Re: Perl RE; how to capture, and replace based on a block?

[educated_foo]

To minimize unhelpful replies here, you should probably do something like this:

1. Add "use strict;" to the top of your code.
2. Add "my ();" right after it.
3. Keep adding "VAR," between the parens in #2 as long as Perl complains about 'Global symbol "VAR"...'

Someone should probably write an Acme:: module to do this automatically.

[taint]

Sorry. I just

cat ./FILE.html | perl {...}

in an open xterm. After several failures, and no more ideas. I closed the xterm, and asked for help. I didn't think it'd be of any use in the request.

I've since read every single reference in the Perl documentation, and while I think I've got the RE part down. I'm quite sure I don't know how to feed Perl the file properly to do any more than eat a single line at a time.

So let me have another go at it. The following

#!/usr/bin/perl -w

#retest.pl
# my feeble attempt to a multi-line RE in Perl

$regexp = shift;
while (<>) {
    print if /$regexp/;
}

won't work as

# ./retest.pl \</\div\>\n\<\/body\> ./FILE.html

because shift will only manage input one line at a time. Attempts to figure how to make use of psed, and s2p, have failed miserably.

Apologies for the previous noise, and thank you for the thoughtful responses.

--Chris

[hdb]

Hi Chris, specifying a regex on the command line seems a difficult thing to do. At least you should be printing your $regexp to see what it contains.

In any case, this code seems to work:

my $str = "
</div>
</body>
";

print "Success\n" if $str =~ /\<\/div\>\n\<\/body\>/;

which suggests that if you slurp in your whole file as a single string (e.g. by unsetting $/), your regex should do its job.

local $/;
my $str = <>;
print "Success\n" if $str =~ /\<\/div\>\n\<\/body\>/;

[taint]

Perl said; Success.

Thanks a million, hdb! Your suggestion has helped me greatly in putting the last piece in my current "puzzle".

Thanks again. I'd like to buy a round of +'s, for the house.

--Chris

UPDATE; I forgot to mention. The reason I was feeding the file to Perl is
1) That's what worked best for me with sed.
2) It seemed the easiest way to experiment getting a correct match with Perl.

[QM]

For fiddling with little bits of code, just use the debugger straight away:

swedish_chef> perl -demo

Loading DB routines from perl5db.pl version 1.32
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

main::(-e:1):   mo
  DB<1> $string = "one two three four"

  DB<2> x $string =~ m/(\w+)/g
0  'one'
1  'two'
2  'three'
3  'four'

Note that "my" variables don't work as expected, I think they get created in the Debug scope, and not in the interpreted scope. But otherwise, have fun in the sandbox.

[taint]

Thank you educated_foo.

" Keep adding "VAR," between the parens in #2 as long as Perl complains about 'Global symbol "VAR"...' Someone should probably write an Acme:: module to do this automatically."

I'll be glad to. Just as soon as I figure this all out. :)

My biggest hangup, I think, is that I'm quite comfortable with sed. But sed is "greedy" by default, and while Perl RE can be. It's not, by default, and that's what I need here (not greedy).

s/\<\/div\>/,/\<\/body\>/

will match my pattern in sed. But it will match from the first </div> till the first </body>. Which is too much.

Thanks again for the response, educated_foo

--Chris

[Laurent_R]

By default, Perl RE are greedy. Have you considered the possibility that the end of line might be more than \n (if the file is coming from Windows, for example)?

[taint]

Greetings, Laurent_R, and thanks for the reply.

Oh yes. I'm keen on the \n v \r v \n\r thing, and you're absolutely correct. Except, in my case, I'm on a *NIX box, and I've written the files myself. So I know they're utf-8 (no BOM), with newlines, no "hard" returns. :)

Maybe it's just the examples I was reading (perlrequick, perlretut, and perlfaq6) but I got the impression that Perl RE wasn't greedy. More Perl RE reading, I guess.

Thanks again, for the response Laurent_R.

--Chris

[Anonymous Monk]

... sed ...

here is my test program

use re 'debug';
$_ = q{</div>
</body>};
print 'does it match ', int m{\<\/div\>\n\<\/body\>};