grep a expression in an array of string with Perl

Question

I'm trying to grep a special pattern in an array of strings.

My array of strings is like this :

@list=("First phrase with \"blabla - Word\" and other things "
      ,"A phrase without... "
      ,"Second phrase with \"truc - Word\" and etc... "
      ,"Another phrase without... "
      ,"Another phrase with \"thing - Word\" and etc... ");

and I tried to grep the pattern "..... - Word" with this function :

@keyw = grep { /\".* Word\"/} (@list);

and I have the following result :

print  (Dumper  (  @keyw));
$VAR1 = 'First phrase with "blabla - Word" and other things ';
$VAR2 = 'Second phrase with "truc - Word" and etc... ';
$VAR3 = 'Another phrase with "thing - Word" and etc... ';

My grep function is ok to grep the phrase but I would like to grep just the pattern and get the following result :

$VAR1 = '"blabla - Word"';
$VAR2 = '"truc - Word"';
$VAR3 = '"thing - Word"';

Do you know how to reach this result ?

Community · Accepted Answer · 2017-05-23 10:34:06Z

4

Use map instead of grep:

my @keyw = map { /\"[^"]*? Word\"/ ? $& : () } @list;

It just returns $& (whole match) if the pattern matches and () (empty list) if it does not.
Little caveat: don't use $& with with Perl < 5.18.0.

Here's Casimir et Hippolyte's simpler solution:

my @keyw = map { /(\"[^"]*? Word\")/ } @list;

It works since m// returns a list of captured groups.

edited May 23, 2017 at 10:34

CommunityBot

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answered Sep 9, 2015 at 19:58

Lucas Trzesniewski

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4 Comments

Casimir et Hippolyte Over a year ago

instead of using the ternary operator and $&, you can use a capture group. See the performance issue about using $&: perldoc.perl.org/perlvar.html . Note that the original pattern can be more waterproof if the dot is replaced (at least) with [^"]

Lucas Trzesniewski Over a year ago

@CasimiretHippolyte hmm... not sure I understand what you're suggesting. Returning anything short of () yields undef values in the resulting array. The performance issue of $& was solved long ago. You're right about [^"].

Casimir et Hippolyte Over a year ago

I was thinking about: my @keyw = map {/(\".* Word\")/} @list;

Lucas Trzesniewski Over a year ago

@CasimiretHippolyte d'oh, I see, thanks :) My Perl is getting rusty.

Matt Jacob · Accepted Answer · 2015-09-09 20:11:49Z

2

Why can't we just use a normal loop?

use strict;
use warnings;

use Data::Dump;

my @phrases = (
    "First phrase with \"blabla - Word\" and other things ",
    "A phrase without... ",
    "Second phrase with \"truc - Word\" and etc... ",
    "Another phrase without... ",
    "Another phrase with \"thing - Word\" and etc... ",
);

my @matches;

for (@phrases) {
    next unless /("[^"]+Word")/;
    push(@matches, $1);
}

# prints ["\"blabla - Word\"", "\"truc - Word\"", "\"thing - Word\""]
dd(\@matches);

answered Sep 9, 2015 at 20:11

Matt Jacob

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