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Re: Pattern matching

by parv (Vicar)
on Nov 10, 2018 at 09:02 UTC ( #1225521=note: print w/replies, xml ) Need Help??


in reply to Pattern matching

Above could not possibly "print[s] the whole line" for "MODULE " will be missing. As you are capturing any- & everything after "MODULE " with "(.*)", so you would get "C17 (N...)" string. Capture what you actually want.

Surely there must be some other patterns besides one specific case? What are they?

In this specific case, try ...

m{ \b (MODULE \s+ [A-Z]+[0-9]+) \s* [(] .+? [)] }x

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Re^2: Pattern matching
by nursyza (Novice) on Nov 10, 2018 at 09:17 UTC

    Thank you. And btw can you explain to me how to read the patterns you wrote?

      m{ # Word boundary. \b # Start capture of pattern matched; ( # literal string "MODULE", MODULE # one or more space characters, \s+ # one or more A-Z letters (represented as character class), [A-Z]+ # one or more 0-9 digits, [0-9]+ # stop capture. ) # Zero or more space characters. \s* # 1-element character class, or "escaped" "(" (not start of captur +e); [(] # any & everything until ... .+? # ... literal ")". [)] }x # /x flag allows to expand the regex as you see above & mentio +ned elsewhere.
      ... can you explain to me how to read the patterns ...

      Because parv's regex contains nothing that is not supported by Perl version 5.6, the YAPE::Regex::Explain module can help.

      c:\@Work\Perl\monks>perl -wMstrict -le "use YAPE::Regex::Explain; ;; my $rx = qr{ \b (MODULE \s+ [A-Z]+[0-9]+) \s* [(] .+? [)] }x; ;; print YAPE::Regex::Explain->new($rx)->explain; " The regular expression: (?x-ims: \b (MODULE \s+ [A-Z]+[0-9]+) \s* [(] .+? [)] ) matches as follows: NODE EXPLANATION ---------------------------------------------------------------------- (?x-ims: group, but do not capture (disregarding whitespace and comments) (case-sensitive) (with ^ and $ matching normally) (with . not matching \n): ---------------------------------------------------------------------- \b the boundary between a word char (\w) and something that is not a word char ---------------------------------------------------------------------- ( group and capture to \1: ---------------------------------------------------------------------- MODULE 'MODULE' ---------------------------------------------------------------------- \s+ whitespace (\n, \r, \t, \f, and " ") (1 or more times (matching the most amount possible)) ---------------------------------------------------------------------- [A-Z]+ any character of: 'A' to 'Z' (1 or more times (matching the most amount possible)) ---------------------------------------------------------------------- [0-9]+ any character of: '0' to '9' (1 or more times (matching the most amount possible)) ---------------------------------------------------------------------- ) end of \1 ---------------------------------------------------------------------- \s* whitespace (\n, \r, \t, \f, and " ") (0 or more times (matching the most amount possible)) ---------------------------------------------------------------------- [(] any character of: '(' ---------------------------------------------------------------------- .+? any character except \n (1 or more times (matching the least amount possible)) ---------------------------------------------------------------------- [)] any character of: ')' ---------------------------------------------------------------------- ) end of grouping ----------------------------------------------------------------------


      Give a man a fish:  <%-{-{-{-<

        Thanks to you & kevbot for posting about YAPE::Regex::Explain. That was what I wanted to do too before posting my explanation.

        In order to use the Y::R::E module installed in my own directory with system perl, I needed to set $PREL5LIB obviously. But ...

        export PERL5LIB="/dir/lib/perl5"

        ... was not enough. I had to add 2 more sub-directories ...

        export PERL5LIB="/dir/lib/perl5:/dir/lib/perl5/site_perl:/dir/lib/perl +5/site_perl/mach"

        ... why could perl not find the last two directory paths by itself in year 2018? (Yes, I am aware the virtues of installing, compiling my own perl. And I love that; had built multiple times on FreeBSD & CentOS.)

      Hi nursyza,

      I see that parv already provided you with an explanation of the regex pattern for you. I wanted to let you know that you can use the YAPE::Regex::Explain module to provide an explanation of any regular expression pattern. Once you have the package installed you can do something like this at the command line to get the explanation for your pattern

      You may also want to look at perlre to get more familiar with regular expressions.

      UPDATE: As parv, soonix, and AnomalousMonk pointed out (in the replies to this node), the above usage of YAPE::Regex::Explain is not correct. Passing the regex as a double-quoted string caused problems.

      The following code gives the correct output

      #!/usr/bin/env perl use strict; use warnings; use YAPE::Regex::Explain; my $re = qr/ \b (MODULE \s+ [A-Z]+[0-9]+) \s* [(] .+? [)] /x; my $exp = YAPE::Regex::Explain->new($re)->explain; print $exp; exit;
      Here is the output
      The regular expression: (?x-ims: \b (MODULE \s+ [A-Z]+[0-9]+) \s* [(] .+? [)] ) matches as follows: NODE EXPLANATION ---------------------------------------------------------------------- (?x-ims: group, but do not capture (disregarding whitespace and comments) (case-sensitive) (with ^ and $ matching normally) (with . not matching \n): ---------------------------------------------------------------------- \b the boundary between a word char (\w) and something that is not a word char ---------------------------------------------------------------------- ( group and capture to \1: ---------------------------------------------------------------------- MODULE 'MODULE' ---------------------------------------------------------------------- \s+ whitespace (\n, \r, \t, \f, and " ") (1 or more times (matching the most amount possible)) ---------------------------------------------------------------------- [A-Z]+ any character of: 'A' to 'Z' (1 or more times (matching the most amount possible)) ---------------------------------------------------------------------- [0-9]+ any character of: '0' to '9' (1 or more times (matching the most amount possible)) ---------------------------------------------------------------------- ) end of \1 ---------------------------------------------------------------------- \s* whitespace (\n, \r, \t, \f, and " ") (0 or more times (matching the most amount possible)) ---------------------------------------------------------------------- [(] any character of: '(' ---------------------------------------------------------------------- .+? any character except \n (1 or more times (matching the least amount possible)) ---------------------------------------------------------------------- [)] any character of: ')' ---------------------------------------------------------------------- ) end of grouping ----------------------------------------------------------------------

        The output of your Y::R::E is much different than the one provided by AnomalousMonk. Yours is missing word boundary (\b) & space characters (\s). Is that due to problem with copy-paste or your version of Y::R::E module?

Re^2: Pattern matching
by nursyza (Novice) on Nov 10, 2018 at 09:14 UTC

    It works now. Thank you!

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