# Regex **URL:** \ **Category:** Ruby\ **Created:** [January 16, 2006, 2:33pm UTC](https://www.ruby-forum.com/t/regex/95291 "2006-01-16T14:33:06Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![tma](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/ed655f/32.png) [@tma](https://www.ruby-forum.com/u/tma)\ **Post date:** [January 16, 2006, 2:33pm UTC](https://www.ruby-forum.com/t/regex/95291/1 "2006-01-16T14:33:06Z")
I’m digging through the Pragmatic Programmers book and had some questions about regex support. Initially they only mention .sub and .gsub. If I wanted to write a regex block using additional flags, say something like this: s/perl/ruby/igsm What that be expressed as: “my favorite programming language is perl”.gsub(/perl/ism, ‘ruby’) ??? What about the ‘x’ option? ---
**Author:** ![tma](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/ed655f/32.png) [@tma](https://www.ruby-forum.com/u/tma)\ **Post date:** [January 16, 2006, 3:06pm UTC](https://www.ruby-forum.com/t/regex/95291/2 "2006-01-16T15:06:14Z")
Hi – On Mon, 16 Jan 2006, Tom A. wrote: > “my favorite programming language is perl”.gsub(/perl/ism, ‘ruby’) > > ??? /s turns on SJIS encoding, so you probably don’t want that. As for all the multiline matching, etc., /m causes the wildcard dot to match newline characters, like /s in Perl. You don’t need an equivalent of Perl’s /m because ^ and $ already always match beginning/end of lines. To match beginning/end of string, you use anchors: \A and \z (or \Z to discount a final newline). > What about the ‘x’ option? What about it? 🙂 It’s there if you want to use it. David – David A. Black removed\_email\_address@domain.invalid “Ruby for Rails”, from Manning Publications, coming April 2006! > **[Ruby for Rails](https://www.manning.com/books/ruby-for-rails)** > > NEWER EDITION AVAILABLE > > The Well-Grounded Rubyist, Second Edition is now available. An eBook of the previous edition, The Well-Grounded Rubyist is included at no additional cost when you buy the revised edition! > > > Ruby for Rails helps Rails... ---
**Author:** ![tma](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/ed655f/32.png) [@tma](https://www.ruby-forum.com/u/tma)\ **Post date:** [January 16, 2006, 4:03pm UTC](https://www.ruby-forum.com/t/regex/95291/3 "2006-01-16T16:03:41Z")
removed\_email\_address@domain.invalid wrote: > /s turns on SJIS encoding, so you probably don’t want that. As for > all the multiline matching, etc., /m causes the wildcard dot to match > newline characters, like /s in Perl. You don’t need an equivalent of > Perl’s /m because ^ and $ already always match beginning/end of lines. > To match beginning/end of string, you use anchors: \A and \z (or \Z to > discount a final newline). There’s a lot of differences to get used to here. I’m surprised that Ruby would go contrary to Perl in the regex flags. It’s bound to be a source of confusion, at least for myself. ---
**Author:** ![tma](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/ed655f/32.png) [@tma](https://www.ruby-forum.com/u/tma)\ **Post date:** [January 16, 2006, 4:12pm UTC](https://www.ruby-forum.com/t/regex/95291/4 "2006-01-16T16:12:47Z")
Hi – On Tue, 17 Jan 2006, Tom A. wrote: > I’m surprised that Ruby would go contrary to Perl in the regex flags. It’s > bound to be a source of confusion, at least for myself. It’s like so many things: if languages just did what older languages did, there would be no point in having new languages 🙂 David – David A. Black removed\_email\_address@domain.invalid “Ruby for Rails”, from Manning Publications, coming April 2006! > **[Ruby for Rails](https://www.manning.com/books/ruby-for-rails)** > > NEWER EDITION AVAILABLE > > The Well-Grounded Rubyist, Second Edition is now available. An eBook of the previous edition, The Well-Grounded Rubyist is included at no additional cost when you buy the revised edition! > > > Ruby for Rails helps Rails... ---
**Author:** ![tma](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/ed655f/32.png) [@tma](https://www.ruby-forum.com/u/tma)\ **Post date:** [January 17, 2006, 1:58am UTC](https://www.ruby-forum.com/t/regex/95291/5 "2006-01-17T01:58:05Z")
> AND here’s a completely new regexp engine coming for 2.0 - fun for the > whole family. > > That said, although it’s undesirable, noone’s obliged to be completely > PCRE-compatible, and it always pays to take five minutes to read the > (IMO pretty clear as far as regexps are concerned) documentation. Considering that PCRE is pretty much a language in itself, it would make life a hell of a lot easier if there was at least some effort to either stick to the established norms of regex engines or at least avoid treading on them in the name of being different. regexp isn’t trivial, making it more varied from language to language isn’t going to help matters much. ---
**Author:** ![tma](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/ed655f/32.png) [@tma](https://www.ruby-forum.com/u/tma)\ **Post date:** [January 17, 2006, 1:58am UTC](https://www.ruby-forum.com/t/regex/95291/6 "2006-01-17T01:58:05Z")
On Mon, 16 Jan 2006 16:01:48 +0100, Tom A. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > It’s bound to be a source of confusion, at least for myself. AND here’s a completely new regexp engine coming for 2.0 - fun for the whole family. That said, although it’s undesirable, noone’s obliged to be completely PCRE-compatible, and it always pays to take five minutes to read the (IMO pretty clear as far as regexps are concerned) documentation. ---
**Author:** ![tma](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/ed655f/32.png) [@tma](https://www.ruby-forum.com/u/tma)\ **Post date:** [January 17, 2006, 4:16am UTC](https://www.ruby-forum.com/t/regex/95291/7 "2006-01-17T04:16:48Z")
On Mon, 16 Jan 2006 22:29:45 +0100, Tom A. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > life a hell of a lot easier if there was at least some effort to either > stick to the established norms of regex engines or at least avoid > treading on them in the name of being different. regexp isn’t trivial, > making it more varied from language to language isn’t going to help > matters much. Well, I think Oniguruma, the new regexp engine, is a bit closer to PCRE in feature availability. And the changes to regexp options don’t seem that catastrophical to me, I’d rather express my intention in the pattern itself than changing its behaviour globally or using option grouping inside it. David V. ---
**Author:** ![tma](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/ed655f/32.png) [@tma](https://www.ruby-forum.com/u/tma)\ **Post date:** [January 17, 2006, 4:19am UTC](https://www.ruby-forum.com/t/regex/95291/8 "2006-01-17T04:19:50Z")
Hi – On Tue, 17 Jan 2006, Tom A. wrote: > Considering that PCRE is pretty much a language in itself, it would make life > a hell of a lot easier if there was at least some effort to either stick to > the established norms of regex engines or at least avoid treading on them in > the name of being different. regexp isn’t trivial, making it more varied > from language to language isn’t going to help matters much. Then you’ll have to blame Perl, for breaking away from sed 🙂 There’s really never been one regex syntax, across all these various languages and utilities; it’s a very, very unlikely area for uniformity. In any case, Perl didn’t necessarily get everything right – for example, it’s nice to have anchors for all possible combinations of start/end and string/line, as Ruby does. (Maybe recent Perls do too; I’m not sure.) David – David A. Black removed\_email\_address@domain.invalid “Ruby for Rails”, from Manning Publications, coming April 2006! > **[Ruby for Rails](https://www.manning.com/books/ruby-for-rails)** > > NEWER EDITION AVAILABLE > > The Well-Grounded Rubyist, Second Edition is now available. An eBook of the previous edition, The Well-Grounded Rubyist is included at no additional cost when you buy the revised edition! > > > Ruby for Rails helps Rails...