Perl Regexp help w/ grep

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

Greetings Fellow Monks:
I am in serious need of your wisdom and help.
The goal is to list the contents of a directory (no problem)
and do something with the files that contain,match via grep to specific patterns; one that will always be at the start of the file, and the other somewhere in the middle of the filename. In other words I want to match a file, for example, that has to contain STR1 at the beginning, and _STR2_ (the underscores are required), somewhere in the middle.
With the correct regex:
STR1some_STR2_file.txt would match
.whereas.
STR1some_STR2file.txt would NOT match
with the code below I have managed to get the qualifier for the beginning of the string to be matched, however to have both matches I have no clue.

#!/usr/bin/perl -w
use strict;
use FileHandle;

my $localdir="C:\\PROJECTS\\";

my $id="LWX1";
opendir LOCALDIR, "$localdir";
my @local_files = grep /^$id/i, readdir LOCALDIR;
###my guess fr both would be this: (doesn't work)
###where "_arbv_" is the 2nd string that must be matched
#my @local_files = grep /^$id&&_arbv_/i, readdir LOCALDIR;
closedir LOCALDIR;

##determine which files to download
    foreach my $local (@local_files)
    {
        
        print "$local\n";
    
    }
[download]

Your help in this matter is greatly appreciated. For I am stumped with this one! Thanks in advance.

Comment on Perl Regexp help w/ grep Download Code

Replies are listed 'Best First'.
Re: Perl Regexp help w/ grep by Roy Johnson (Monsignor) on Oct 14, 2005 at 17:11 UTC
For that, I'd say go with a file glob rather than explicit opendir/readdir/grep. `my @local_files = glob('STR1_STR2_');` [download] Caution: Contents may have been coded under pressure.	[reply] [d/l]
Re: Perl Regexp help w/ grep by VSarkiss (Monsignor) on Oct 14, 2005 at 17:40 UTC
Very close. An easy way to do it like you're thinking: `my @local_files = grep { /^$id/i && /_arbv_/i } readdir LOCAlDIR;` [download] For more info, check out grep Note, this is untested. Do not rebuke them with harsh words ... but rather lead them gently - with URLs - so that they may learn wisdom.	[reply] [d/l]
Re: Perl Regexp help w/ grep by injunjoel (Priest) on Oct 14, 2005 at 17:08 UTC
Greetings all, Here is my suggestion. `#the following is untested. my @local_files = grep /^$id.?_arbv_/i, readdir LOCALDIR;` [download] The `.` matches any character. The `` matches the previous character 0 or more times and the `?` keeps it from being too greedy (well in concert with `` that is*) So it matches the shortest amount possible not the longest. -InjunJoel "I do not feel obliged to believe that the same God who endowed us with sense, reason and intellect has intended us to forego their use." -Galileo	[reply] [d/l] [select]
Re^2: Perl Regexp help w/ grep by revdiablo (Prior) on Oct 14, 2005 at 19:00 UTC
the ? keeps it from being too greedy I'm curious, what is the purpose of including this in a simple match? Seems to me that it would only make sense if it was a capturing match or a search and replace. Not that there's anything wrong with it, it just seems a bit pointless.	[reply]
Re^3: Perl Regexp help w/ grep by duff (Parson) on Oct 15, 2005 at 03:52 UTC
Perhaps it's an attempt at optimization? A greedy RE will match the entire filename from that point on and then have to back track character by character to determine if there is or isn't a match. By making the RE non-greedy, matching filenames will be found faster. duff	[reply]