# Gsub("\\\\", "\\\\\\\\") seems unintuitive **URL:** \ **Category:** Ruby\ **Created:** [February 22, 2008, 6:28pm UTC](https://www.ruby-forum.com/t/gsub-seems-unintuitive/129919 "2008-02-22T18:28:40Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![princenamor](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/c0e974/32.png) [@princenamor](https://www.ruby-forum.com/u/princenamor)\ **Post date:** [February 22, 2008, 6:28pm UTC](https://www.ruby-forum.com/t/gsub-seems-unintuitive/129919/1 "2008-02-22T18:28:40Z")
The following confusing behavior is noted in the pickaxe book (2nd ed) on page 75: # I would expect two backslashes in the result irb\> puts “\”.gsub("\","\\") \ # I would expect four backslashes in the result irb\> puts “\”.gsub("\","\\\\") \ I can certainly work around it, but it seems unintuitive. Is there a reason why gsub behaves this way? Just curious… ---
**Author:** ![princenamor](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/c0e974/32.png) [@princenamor](https://www.ruby-forum.com/u/princenamor)\ **Post date:** [February 22, 2008, 6:37pm UTC](https://www.ruby-forum.com/t/gsub-seems-unintuitive/129919/2 "2008-02-22T18:37:56Z")
John W. wrote: > The following confusing behavior is noted in the pickaxe book (2nd ed) > on page 75: > > # I would expect two backslashes in the result > > irb\> puts “\”.gsub("\","\\") > \ > > # I would expect four backslashes in the result > > irb\> puts “\”.gsub("\","\\\\") > \ > > I can certainly work around it, but it seems unintuitive. Is there a > reason why gsub behaves this way? Just curious… It’s not a gsub thing, per se–it’s a string thing. Backslashes are used in strings to escape special characters. One such character is a " mark. If you want to write a " mark in the middle of a string, you have to escape it with a backslash: “They call me “Mellow Yellow” etc.” If you didn’t, then the " would signify the end of the string! Similarly, in the example you listed, if you just did: “” then you end up with a string that ISN’T ended! Because you escaped the next ". So, if you want a literal backslash, you have to escape the backslash too: “\” It just looks confusing because you are escaping the escape character 🙂 ---
**Author:** ![princenamor](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/c0e974/32.png) [@princenamor](https://www.ruby-forum.com/u/princenamor)\ **Post date:** [February 22, 2008, 6:41pm UTC](https://www.ruby-forum.com/t/gsub-seems-unintuitive/129919/3 "2008-02-22T18:41:05Z")
On Feb 22, 11:27 am, John W. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > I can certainly work around it, but it seems unintuitive. Is there a > reason why gsub behaves this way? Just curious… puts “\”.gsub(“\”){“\\”} ---
**Author:** ![princenamor](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/c0e974/32.png) [@princenamor](https://www.ruby-forum.com/u/princenamor)\ **Post date:** [February 22, 2008, 6:49pm UTC](https://www.ruby-forum.com/t/gsub-seems-unintuitive/129919/4 "2008-02-22T18:49:20Z")
On Feb 22, 2008, at 12:27 PM, John W. wrote: > I can certainly work around it, but it seems unintuitive. Is there a > reason why gsub behaves this way? Just curious… Notwithstanding the earlier responses… Since the replacement string is evaluated ‘twice’, once as a ruby string literal and then again by gsub to look for group refrences like ‘\1’, you need to provide two levels of escaping for a backslash. \ is “\” so two of them is “\\” and you want gsub to see that so it need to have them escaped: “\\\ \” Whew! Yeah, it’s unfortunate, but backslash is doing double-duty here: introducing a group reference to the regular expression and escaping characters in a string literal (just like “\n”, but also itself). -Rob Rob B. [http://agileconsultingllc.com](http://agileconsultingllc.com) removed\_email\_address@domain.invalid ---
**Author:** ![princenamor](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/c0e974/32.png) [@princenamor](https://www.ruby-forum.com/u/princenamor)\ **Post date:** [February 22, 2008, 6:54pm UTC](https://www.ruby-forum.com/t/gsub-seems-unintuitive/129919/5 "2008-02-22T18:54:37Z")
Just as a side note, this is typical in all real programming languages. C, C++, Java, Perl, sh, etc. I _believe_ it’s also true in python, lithp/scheme, & (o)caml, but for those I’ve either not used them, or not used them in so long I’m unsure. Some languages, like vb{[6|script|.net](http://6%7Cscript%7C.net)}, use a doubled quote, but those aren’t really proper programing languages 😉 –Kyle ---
**Author:** ![princenamor](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/c0e974/32.png) [@princenamor](https://www.ruby-forum.com/u/princenamor)\ **Post date:** [February 22, 2008, 7:01pm UTC](https://www.ruby-forum.com/t/gsub-seems-unintuitive/129919/6 "2008-02-22T19:01:45Z")
Thanks Rob, that’s exactly what I was missing – the second round of escaping is necessary to make escaped references to regex groups work. ---
**Author:** ![princenamor](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/c0e974/32.png) [@princenamor](https://www.ruby-forum.com/u/princenamor)\ **Post date:** [December 17, 2008, 10:15pm UTC](https://www.ruby-forum.com/t/gsub-seems-unintuitive/129919/7 "2008-12-17T22:15:40Z")
I stumbled onto this thread trying to figure out a similar problem… ---
**Author:** ![princenamor](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/c0e974/32.png) [@princenamor](https://www.ruby-forum.com/u/princenamor)\ **Post date:** [December 17, 2008, 10:19pm UTC](https://www.ruby-forum.com/t/gsub-seems-unintuitive/129919/8 "2008-12-17T22:19:52Z")
Joe P. wrote: > I stumbled onto this thread trying to figure out a similar problem… Dangit, I didn’t mean to post the above message 🙂 Okay, I need to read a site name (like “[joe.com](http://joe.com)”) and put a \ in front of the period (so it would be “joe.com”). I’m having trouble with this, I can’t seem to get only ONE \ in front of the period… > > “[joe.com](http://joe.com)”.gsub(/./, “\.”) > > =\> “joe\.com” > > “[joe.com](http://joe.com)”.gsub(/./, “\\.”) > > =\> “joe\.com” Anyone have a clue what to do? I’m probably missing something simple. ---
**Author:** ![princenamor](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/c0e974/32.png) [@princenamor](https://www.ruby-forum.com/u/princenamor)\ **Post date:** [December 17, 2008, 10:29pm UTC](https://www.ruby-forum.com/t/gsub-seems-unintuitive/129919/9 "2008-12-17T22:29:32Z")
On Wed, Dec 17, 2008 at 2:12 PM, Joe P. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > =\> “joe\.com” > > > > “[joe.com](http://joe.com)”.gsub(/./, “\\.”) > > > =\> “joe\.com” > > ## Anyone have a clue what to do? I’m probably missing something simple. > > Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/). That’s because you are in irb. You are getting what you want try this: puts “[joe.com](http://joe.com)”.gsub(/./, “\\.”) Actually it might be more readable as gsub(‘.’, ‘.’) – “Hey brother Christian with your high and mighty errand, Your actions speak so loud, I can’t hear a word you’re saying.” -Greg Graffin (Bad Religion) ---
**Author:** ![princenamor](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/c0e974/32.png) [@princenamor](https://www.ruby-forum.com/u/princenamor)\ **Post date:** [December 18, 2008, 4:20pm UTC](https://www.ruby-forum.com/t/gsub-seems-unintuitive/129919/10 "2008-12-18T16:20:47Z")
Okay, those last two explanations helped clear up my confusion. Thanks. ---
**Author:** ![princenamor](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/c0e974/32.png) [@princenamor](https://www.ruby-forum.com/u/princenamor)\ **Post date:** [December 18, 2008, 12:06am UTC](https://www.ruby-forum.com/t/gsub-seems-unintuitive/129919/11 "2008-12-18T00:06:13Z")
On Wed, Dec 17, 2008 at 3:12 PM, Joe P. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > =\> “joe\.com” > > > > “[joe.com](http://joe.com)”.gsub(/./, “\\.”) > > > =\> “joe\.com” > > Anyone have a clue what to do? I’m probably missing something simple. You are looking at a string with escaping characters (i.e. what it would look like in double quotes). You can verify this by using #puts or “[joe.com](http://joe.com)”.gsub(‘.’, ‘.’).length. hth, Todd