Match upper and lower case

[benlaw]

Hi all,
I am using regular expression to match some words which may lower or upper case, such as "Error", "ERROR", "error", "ErroR".. . I just looking for search any "error" in the message , is there any method?
thx a lot

[Zaxo]

Use the /i flag for case-insensitive match.

if (/error/i) {
    #. . .
}

or

my $erre = qr/error/i;
$str =~ $erre snd # . . .

[jimrobertsiii]

IMHO TMTOWTDI


if (uc $error eq "ERROR"){
   # . . .
}

or

if (lc $error eq "error"){
   # . . .
}

Although, I would prefer Zaxo's first example because it seems more efficient (if for no other reason, but conservation of code :-)

[blazar]

IMHO TMTOWTDI

if (uc $error eq "ERROR"){
   # . . .
}

or

if (lc $error eq "error"){
   # . . .
}

Although, I would prefer Zaxo's first example because it seems more efficient (if for no other reason, but conservation of code :-)

Note that this is not strictly equivalent to Zaxo's code since /error/i checks (case insensitively) for the presence of the string 'error' and not for equality to it (up to case insentiveness).

More importantly: "more efficient"? Well, I premise that I'd probably use /error/i or /^error$/i (this really depends on what can there be in $_) myself in most reasonable cases, but running

#!/usr/bin/perl

use strict;
use warnings;
use Benchmark qw/:all :hireswallclock/;

my $test_str='error';
my @test=map {
    my @chr=("\0", " ");
    local $_=$test_str;
    s/./$& ^ $chr[rand 2]/ge} 1..100;

no warnings 'void';
cmpthese -30, { regex => sub { /^\Q$test_str\E$/i for @test },
                lc => sub { $test_str eq lc for @test} }, 'all';

__END__

I get

Benchmark: running lc, regex for at least 30 CPU seconds...
        lc: 34.068 wallclock secs (34.10 usr  0.00 sys +  0.00 cusr  0
+.00 csys = 34.10 CPU) @ 19917.24/s (n=679178)
     regex: 31.518 wallclock secs (31.53 usr  0.00 sys +  0.00 cusr  0
+.00 csys = 31.53 CPU) @ 13689.50/s (n=431630)
         Rate regex    lc
regex 13690/s    --  -31%
lc    19917/s   45%    --

and

Benchmark: running lc, regex for at least 30 CPU seconds...
        lc: 31.4462 wallclock secs (31.45 usr  0.00 sys +  0.00 cusr  
+0.00 csys = 31.45 CPU) @ 26138.57/s (n=822058)
     regex: 31.8579 wallclock secs (31.86 usr  0.00 sys +  0.00 cusr  
+0.00 csys = 31.86 CPU) @ 14326.49/s (n=456442)
         Rate regex    lc
regex 14326/s    --  -45%
lc    26139/s   82%    --

under Windows 98 and Linux (kernel 2.6.10) respectively. Perl 5.8.6 in both cases...

[gopalr]

Hi,

use 'i' for ignore case.

if ($_=~m#error#i)   
{
  ..  ## It'll match whole 'error'
}

[jbrugger]

I downvoted you here, i strongly believe that these kind of questions can be found if a little effort would be put in searching older nodes, google, perldoc, books etc. (and so you learn more too!)
This is imho not a question belonging here anymore (and cirtenly not at The Monastery Gates), thinking, reading and searching should be done before asking, this is lazy.

[foil]

Jbrugger, I agree, but maybe the better question is why this question was approved and front-paged ?? node_id=17688 explains the process . Not the first loose approval lately, I think .

[ysth]

Nothing wrong with approving this node that I can see. If we didn't approve questions that could be self-answered by 30 or less minutes of searching/reading, we wouldn't have very many approved questions.

[DrHyde]

It's at least possible that someone might have looked for documentation but because they were using the wrong keywords not have found anything useful. However, I too downvoted this node because the poster didn't even say that he had looked, let alone where he had looked.