Grep match alternative

IB2017 has asked for the wisdom of the Perl Monks concerning the following question:

Dear monks

I need to read the files contained in a directory and select them according to their extensions. I'd like to use grep as it seems to be a very fast and concise solution, but I am having problems in matching more than one extention at a time. How can improve the following (it doesn't produce any result, the problem being in the regexp in combination with grep)?

    opendir (DIR, "$MyDir") or die "$!";
        my @Documents = grep {/\.[docx|pdf]$/}  readdir DIR;
        my $number_of_files = scalar @Documents;
        print "Total number of files found in folder: $number_of_files
+\n";
    close DIR;
[download]

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Re: Grep match alternative by pryrt (Abbot) on Oct 11, 2017 at 20:57 UTC
See perlre. `[]` is a character class (perlrecharclass): `c:\>perl -le "print $_, qq(\t), /\.[docx\|pdf]$/ \|\|0 for qw(.pdf .docx +.p .d .f .d .o .c .x .\|);" .pdf 0 .docx 0 .p 1 .d 1 .f 1 .d 1 .o 1 .c 1 .x 1 .\| 1` [download] `(?:)` is a non-capturing group: `c:\>perl -le "print $_, qq(\t), /\.(?:docx\|pdf)$/ \|\|0 for qw(.pdf .doc +x .p .d .f .d .o .c .x .\|);" .pdf 1 .docx 1 .p 0 .d 0 .f 0 .d 0 .o 0 .c 0 .x 0 .\| 0` [download] edit: fix typo (missing "?:" in my second one-liner)	[reply] [d/l] [select]
Re^2: Grep match alternative by IB2017 (Pilgrim) on Oct 11, 2017 at 21:02 UTC
Perfect explanation, thank you!	[reply]
Re^3: Grep match alternative by AnomalousMonk (Archbishop) on Oct 11, 2017 at 21:30 UTC
Your regex is simple enough (i.e., it uses no regex construct introduced after Perl version 5.6) that the hoary YAPE::Regex::Explain can still be informative: c:\@Work\Perl\monks>perl -wMstrict -le "use YAPE::Regex::Explain; ;; print YAPE::Regex::Explain->new(qr/\.[docx\|pdf]$/)->explain; " The regular expression: (?-imsx:\.[docx\|pdf]$) matches as follows: NODE EXPLANATION ---------------------------------------------------------------------- (?-imsx: group, but do not capture (case-sensitive) (with ^ and $ matching normally) (with . not matching \n) (matching whitespace and # normally): ---------------------------------------------------------------------- \. '.' ---------------------------------------------------------------------- [docx\|pdf] any character of: 'd', 'o', 'c', 'x', '\|', 'p', 'd', 'f' ---------------------------------------------------------------------- $ before an optional \n, and the end of the string ---------------------------------------------------------------------- ) end of grouping ---------------------------------------------------------------------- [download] See also perlretut, and perlrequick. Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]
Re: Grep match alternative by karlgoethebier (Abbot) on Oct 12, 2017 at 09:43 UTC
"... concise solution..." Consider this TMTOWTDI: `#!/usr/bin/env perl use strict; use warnings; use Path::Iterator::Rule; use Data::Dump; use feature qw (say); my $rule = Path::Iterator::Rule->new; $rule->or( $rule->new->name(".pdf"), $rule->new->name(".docx") ); my @matches = $rule->all(q(.)); dd \@matches; say scalar @matches; __END__` [download] N.B.: Written in a hurry and not thoroughly tested, but it should work. Regards, Karl ŤThe Crux of the Biscuit is the Apostropheť `perl -MCrypt::CBC -E 'say Crypt::CBC->new(-key=>'kgb',-cipher=>"Blowfish")->decrypt_hex($ENV{KARL});'`Help	[reply] [d/l] [select]
Re: Grep match alternative by Anonymous Monk on Oct 11, 2017 at 20:49 UTC
try parens instead of brackets.	[reply]
Re^2: Grep match alternative by IB2017 (Pilgrim) on Oct 11, 2017 at 21:01 UTC
Thank you.	[reply]