# Dumb str.sub question **URL:** \ **Category:** ruby-talk\ **Created:** [26 November 2003 18:08 UTC](https://rubytalk.org/t/dumb-str-sub-question/9061 "2003-11-26T18:08:17Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Orion\_Hunter](https://avatars.discourse-cdn.com/v4/letter/o/f1d935/32.png) [@Orion\_Hunter](https://rubytalk.org/u/Orion_Hunter)\ **Post date:** [26 November 2003 18:08 UTC](https://rubytalk.org/t/dumb-str-sub-question/9061/1 "2003-11-26T18:08:17Z")
I feel really dumb asking this, but I just can’t seem to figure it out. I am trying to parse some text for use in a mysql insert statement. That being the case, I need to escape out quote characters. If str= “isn’t stands for is not”, what I want is a string with “isn’t stands for is not” At first I thought, sure, no problem!! But I can’t get it. I’ve tried the following: irb:1\> str = "isn’t stands for is not" irb:2\> str.sub( ‘’’, ‘’’ ) --\> “isn’t stands for is not” (expected) irb:3\> str.sub( ‘’’, ‘\’’ ) --\> unterminated string (expected) irb:4\> str.sub( ‘’’, ‘\’ ) --\> “isnt stands for is nott stands for is not” (huh? Why this wierd double take?) irb:5\> str.sub( ‘’’ ){ |m| m = “’” } --\> “isn’t stands for is not” (expected) irb:6\> str.sub( ‘’’ ){ |m| m = “\’” } --\> “isn\'t stands for is not” (why did it insert TWO 's?, and not just one? I would have exected the first one to “escape” the second, thus giving ’ as desired) So, my quesitons are: 1. How do I do my escape character substituion 2. Why did #4 and #6 behave as they did? Thanks. > **···** > > * * * > > Gift-shop online from the comfort of home at MSN Shopping! No crowds, free > parking. [http://shopping.msn.com](http://shopping.msn.com) ---
**Author:** ![Mark\_J\_Reed](https://avatars.discourse-cdn.com/v4/letter/m/f6c823/32.png) [@Mark\_J\_Reed](https://rubytalk.org/u/Mark_J_Reed)\ **Post date:** [26 November 2003 18:47 UTC](https://rubytalk.org/t/dumb-str-sub-question/9061/2 "2003-11-26T18:47:12Z")
> irb:1\> str = “isn’t stands for is not” > irb:4\> str.sub( ‘'’, '\' ) → “isnt stands for is nott stands for is > not” (huh? Why this wierd double take?) Because of the extra processing that substution strings undergo. Within the substitution, & is replaced by the portion of the original string which matched; ` by the portion before the match; and ' by the portion after. So in your case you have this: ``` SEQUENCE REPLACED BY \` isn \& ' \' t stands for is not ``` > irb:6\> str.sub( ‘'’ ){ |m| m = “\'” } → “isn\'t stands for is not” > (why did it insert TWO \s?, and not just one? I would have exected the > first one to “escape” the second, thus giving ' as desired) It DIDN’T insert two backslashes; it inserted one, which shows up in the inspection of a string as two becuase the inspection uses the double-quote syntax. If you print the string out with puts or otherwise look into it, you’ll see that there is only one backslash: ``` irb(main):007:0> x = str.sub( '\'' ){ |m| m = "\\'" } => "isn\\'t stands for is not" irb(main):008:0> puts x isn\'t stands for is not => nil irb(main):009:0> x[2,1] => "n" irb(main):010:0> x[3,1] => "\\" irb(main):011:0> x[4,1] => "'" ``` By the way, you can simplify to just this: ``` irb(main):006:0> str.sub(/'/) { '\\\'' } => "isn\\'t stands for is not" ``` And you can also use the string form if you use the proper number of backslashes: ``` irb(main):002:0> str.sub(/'/, '\\\\\'') => "isn\\'t stands for is not" ``` -Mark > **···** > > On Thu, Nov 27, 2003 at 03:08:17AM +0900, Orion Hunter wrote: ---
**Author:** ![Austin\_Ziegler2](https://avatars.discourse-cdn.com/v4/letter/a/ad7895/32.png) [@Austin\_Ziegler2](https://rubytalk.org/u/Austin_Ziegler2)\ **Post date:** [26 November 2003 18:50 UTC](https://rubytalk.org/t/dumb-str-sub-question/9061/3 "2003-11-26T18:50:56Z")
str = "isn’t stands for is not" puts str.sub(/’/) { “\’” } #=\> isn’t stands for is not After execution, irb prints an #inspect on the resulting object. -austin > **···** > > – > austin ziegler \* [austin@halostatue.ca](mailto:austin@halostatue.ca) \* Toronto, ON, Canada > software designer \* pragmatic programmer \* 2003.11.26 > \* 13.48.12 ---
**Author:** ![Mike\_Stok](https://avatars.discourse-cdn.com/v4/letter/m/50afbb/32.png) [@Mike\_Stok](https://rubytalk.org/u/Mike_Stok)\ **Post date:** [26 November 2003 19:22 UTC](https://rubytalk.org/t/dumb-str-sub-question/9061/4 "2003-11-26T19:22:22Z")
In article [20031126184634.GB1520@mulan.thereeds.org](mailto:20031126184634.GB1520@mulan.thereeds.org), > **···** > > Mark J. Reed [markjreed@mail.com](mailto:markjreed@mail.com) wrote: > > > irb(main):006:0\> str.sub(/'/) { ‘\'’ } > > =\> “isn\'t stands for is not” > > Sometimes it is useful to pick your quotes carefully e.g. > > str.sub(/'/) { ‘\'’ } > > as you’re quoting a single quote then using double quotes saves a \ > > str.sub(/‘/) { "\’" } > > Mike > > – > [mike@stok.co.uk](mailto:mike@stok.co.uk) | The “`Stok’ disclaimers” apply. > [http://www.stok.co.uk/~mike/](http://www.stok.co.uk/~mike/) | GPG PGP Key 1024D/059913DA > [mike@exegenix.com](mailto:mike@exegenix.com) | Fingerprint 0570 71CD 6790 7C28 3D60 > [http://www.exegenix.com/](http://www.exegenix.com/) | 75D2 9EC4 C1C0 0599 13DA ---
**Author:** ![Mark\_J\_Reed](https://avatars.discourse-cdn.com/v4/letter/m/f6c823/32.png) [@Mark\_J\_Reed](https://rubytalk.org/u/Mark_J_Reed)\ **Post date:** [26 November 2003 19:47 UTC](https://rubytalk.org/t/dumb-str-sub-question/9061/5 "2003-11-26T19:47:11Z")
Good point. I generally make a habit of using single quotes when I’m not doing any interpolation and double-quotes when I am, but this would be a logical place to make an exception. 🙂 -Mark > **···** > > On Wed, Nov 26, 2003 at 07:17:55PM +0000, Mike Stok wrote: > > > Sometimes it is useful to pick your quotes carefully e.g. > > > > str.sub(/'/) { ‘\'’ } > > > > as you’re quoting a single quote then using double quotes saves a \ > > > > str.sub(/‘/) { "\’" }