# About a regular expression **URL:** \ **Category:** Ruby\ **Created:** [November 26, 2007, 11:02pm UTC](https://www.ruby-forum.com/t/about-a-regular-expression/121332 "2007-11-26T23:02:26Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![t5in9tao](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/96bed5/32.png) [@t5in9tao](https://www.ruby-forum.com/u/t5in9tao)\ **Post date:** [November 26, 2007, 11:02pm UTC](https://www.ruby-forum.com/t/about-a-regular-expression/121332/1 "2007-11-26T23:02:26Z")
Hi, I really don’t unserstand why my regular expression don’t scan a string. My goal is to match in a string a domain name. I copy/past my code here: * * * #! /usr/bin/env ruby domain\_name = “[a-zA-Z0-9-]{1,63}.(aero|biz|cat|com|coop|edu|gov|info|int|jobs|mil|mobi|museum|name|net|org|travel|ac|ad|ae|af|ag|ai|al|am|an|ao|aq|ar|as|at|au|aw|az|ba|bb|bd|be|bf|bg|bh|bi|bj|bm|bn|bo|br|bs|bt|bv|bw|by|bz|ca|cc|cd|cf|cg|ch|ci|ck|cl|cm|cn|co|cr|cs|cu|cv|cx|cy|cz|de|dj|dk|dm|do|dz|ec|ee|eg|eh|er|es|et|eu|fi|fj|fk|fm|fo|fr|ga|gb|gd|ge|gf|gg|gh|gi|gl|gm|gn|gp|gq|gr|gs|gt|gu|gw|gy|hk|hm|hn|hr|ht|hu|id|ie|il|im|in|io|iq|ir|is|it|je|jm|jo|jp|ke|kg|kh|ki|km|kn|kp|kr|kw|ky|kz|la|lb|lc|li|lk|lr|ls|lt|lu|lv|ly|ma|mc|md|me|mg|mh|mk|ml|mm|mn|mo|mp|mq|mr|ms|mt|mu|mv|mw|mx|my|mz|na|nc|ne|nf|ng|ni|nl|no|np|nr|nu|nz|om|pa|pe|pf|pg|ph|pk|pl|pm|pn|pr|ps|pt|pw|py|qa|re|ro|rs|ru|rw|sa|sb|sc|sd|se|sg|sh|si|sj|sk|sl|sm|sn|so|sr|st|su|sv|sy|sz|tc|td|tf|tg|th|tj|tk|tl|tm|tn|to|tp|tr|tt|tv|tw|tz|ua|ug|uk|um|us|uy|uz|va|vc|ve|vg|vi|vn|vu|wf|ws|ye|yt|yu|za|zm|zr|zw)” string = “ **\Haïku** ” result = string.scan(/#{domain\_name}/) result.each { |x| puts x } * * * About me, there is a trouble near the dot. But normaly it’s okay thanks to “.” … Thank you for help. ---
**Author:** ![t5in9tao](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/96bed5/32.png) [@t5in9tao](https://www.ruby-forum.com/u/t5in9tao)\ **Post date:** [November 26, 2007, 11:05pm UTC](https://www.ruby-forum.com/t/about-a-regular-expression/121332/2 "2007-11-26T23:05:05Z")
Note: in this example, I would like to save “[haiku-os.org](http://haiku-os.org)” string in result variable. ---
**Author:** ![t5in9tao](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/96bed5/32.png) [@t5in9tao](https://www.ruby-forum.com/u/t5in9tao)\ **Post date:** [November 26, 2007, 11:55pm UTC](https://www.ruby-forum.com/t/about-a-regular-expression/121332/3 "2007-11-26T23:55:46Z")
On Nov 26, 4:02 pm, T5in9tao Tsingtao [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > “[a-zA-Z0-9-]{1,63}.(aero|biz|cat|com|coop|edu|gov|info|int|jobs|mil|mobi|museum|name|net|org|travel|ac|ad|ae|af|ag|ai|al|am|an|ao|aq|ar|as|at|au|aw|az|ba|bb|bd|be|bf|bg|bh|bi|bj|bm|bn|bo|br|bs|bt|bv|bw|by|bz|ca|cc|cd|cf|cg|ch|ci|ck|cl|cm|cn|co|cr|cs|cu|cv|cx|cy|cz|de|dj|dk|dm|do|dz|ec|ee|eg|eh|er|es|et|eu|fi|fj|fk|fm|fo|fr|ga|gb|gd|ge|gf|gg|gh|gi|gl|gm|gn|gp|gq|gr|gs|gt|gu|gw|gy|hk|hm|hn|hr|ht|hu|id|ie|il|im|in|io|iq|ir|is|it|je|jm|jo|jp|ke|kg|kh|ki|km|kn|kp|kr|kw|ky|kz|la|lb|lc|li|lk|lr|ls|lt|lu|lv|ly|ma|mc|md|me|mg|mh|mk|ml|mm|mn|mo|mp|mq|mr|ms|mt|mu|mv|mw|mx|my|mz|na|nc|ne|nf|ng|ni|nl|no|np|nr|nu|nz|om|pa|pe|pf|pg|ph|pk|pl|pm|pn|pr|ps|pt|pw|py|qa|re|ro|rs|ru|rw|sa|sb|sc|sd|se|sg|sh|si|sj|sk|sl|sm|sn|so|sr|st|su|sv|sy|sz|tc|td|tf|tg|th|tj|tk|tl|tm|tn|to|tp|tr|tt|tv|tw|tz|ua|ug|uk|um|us|uy|uz|va|vc|ve|vg|vi|vn|vu|wf|ws|ye|yt|yu|za|zm|zr|zw)” > > ## Thank you for help. > > Posted viahttp://www.ruby-forum.com/. Since your first “.” is inside a double-quoted string, it being put in the regex as just “.”. Either define domain\_name with “\.” in place of “.” or use single quotes instead of double. Or you could define domain\_name to be the regex: domain\_name = /[a-zA-Z0-9-]{1,63}.(aero|biz|cat|[long regex cut]/ … result = string.scan(domain\_name) ---
**Author:** ![t5in9tao](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/96bed5/32.png) [@t5in9tao](https://www.ruby-forum.com/u/t5in9tao)\ **Post date:** [November 27, 2007, 1:15am UTC](https://www.ruby-forum.com/t/about-a-regular-expression/121332/4 "2007-11-27T01:15:53Z")
On Nov 26, 4:34 pm, T5in9tao Tsingtao [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > result.each { |x| puts x } > domain\_name = /[a-zA-Z0-9-]{1,63}.(?:aero|biz|com|org)/ If a regular expression has capture groups in it, String#scan returns those groups, not the entire matched expression. Placing the ?: inside the parentheses instructs Ruby not to treat the contents as a capture group. ---
**Author:** ![t5in9tao](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/96bed5/32.png) [@t5in9tao](https://www.ruby-forum.com/u/t5in9tao)\ **Post date:** [November 27, 2007, 1:26am UTC](https://www.ruby-forum.com/t/about-a-regular-expression/121332/5 "2007-11-27T01:26:38Z")
Gavin K. wrote: > On Nov 26, 4:34 pm, T5in9tao Tsingtao [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > > result.each { |x| puts x } > > domain\_name = /[a-zA-Z0-9-]{1,63}.(?:aero|biz|com|org)/ > > If a regular expression has capture groups in it, String#scan returns > those groups, not the entire matched expression. Placing the ?: inside > the parentheses instructs Ruby not to treat the contents as a capture > group. Thank you Gavin K.! That’s working perfectly. ---
**Author:** ![t5in9tao](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/96bed5/32.png) [@t5in9tao](https://www.ruby-forum.com/u/t5in9tao)\ **Post date:** [November 27, 2007, 12:34am UTC](https://www.ruby-forum.com/t/about-a-regular-expression/121332/6 "2007-11-27T00:34:19Z")
Thank you. But I belive that don’t work yet, even if I update the code like this: * * * domain\_name = /[a-zA-Z0-9-]{1,63}.(aero|biz|com|org)/ string = ‘ **[Haïku](http://haiku-os.org)** ’ result = string.scan(domain\_name) result.each { |x| puts x } * * *