perl regular expression

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

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Re: perl regular expression by GrandFather (Saint) on Oct 03, 2006 at 10:48 UTC
Now that code tags have been added to your node so that the code is clear, the problem also is clear. You are using `[]` in the regex which means match any of the characters within the square brackets. The fix is almost easy - use a non-capture group (`(?:...)`): `if ($filename =~ /(\.(?:htm\|html\|txt\|pdf\|ppt\|csv\|doc]))\b/i)` [download] Note that the repeat (`{3,4}`) is not needed. DWIM is Perl's answer to Gödel	[reply] [d/l] [select]
Re^2: perl regular expression by reasonablekeith (Deacon) on Oct 03, 2006 at 14:45 UTC
I know the OP had the word boundry match at the end, but I don't see its use here. Neither do I see the need for a non capturing group. Either way, the OP should probably positively match for the end of the file name, otherwise one might end up passing a file by virtue of a match part way through the filename. The following wont print match... `my $filename = "/home/root/this_is_a_valid_name.html.gz"; if ($filename =~ m/(\.(htm\|html\|txt\|pdf\|ppt\|csv\|doc))$/i) { print "match\n"; # this won't print }` [download] ... however swap in the this one, and is passes just fine... `my $filename = "/home/root/this_is_a_valid_name.html.gz"; if ($filename =~ /(\.(?:htm\|html\|txt\|pdf\|ppt\|csv\|doc]))\b/i) { print "match\n"; # this will print }` [download] --- my name's not Keith, and I'm not reasonable.	[reply] [d/l] [select]
Re^3: perl regular expression by chargrill (Parson) on Oct 03, 2006 at 18:15 UTC
What happens when the filename is (arbitrarily contrived, but): `magical.html_parser.dll`? Though I suppose it matters what the OP wants to do with the file(s), and whether or not a .gz'd html/txt/etc file is desired. --chargrill `s*lil; $=join'',sort split q; s;.;grr; &&s+(.(.)).+$2$1+; $; = qq-$_-;s,.,ahc,;$,.=chop for split q,,,reverse;print for($,,$;,$,$/)` [download]	[reply] [d/l] [select]
Re: perl regular expression by rminner (Chaplain) on Oct 03, 2006 at 07:08 UTC
Hi, ~~`doc{3,4}` matches doccc and docccc. Another thing is, that you should move the `\.` outside the parentheses.~~ Update: I somehow missed the square brackets. It's just like Grandfather said(Re: perl regular expression). Next time i'll try to focus a bit more while looking at the regex ... Well, at least the example i gave was correct :). I'll give you an example programm: `use strict; use warnings; my $dirname = "/home/hfob"; opendir my $DH , $dirname or die "failed to open $dirname ($!)\n"; my @files = grep { /\.(html?\|txt\|pdf\|ppt\|csv\|doc)$/i} readdir $DH; print "$_\n" for @files; closedir $DH;` [download] If you also want to match files which have a format .txt.<some_other_extension>, you could adapt the grep like follows: `my @files = grep { /\.(html?\|txt\|pdf\|ppt\|csv\|doc)(\.\|$)/i} readdir $DH +;` [download] Then it will accept end of string (in your case the filename), or a dot after the extension. An example for such a case could be myfile.txt.gz	[reply] [d/l] [select]