From: Justin Collins <justincollins@...>
Date: 2010-10-04T12:51:36+09:00
Subject: Re: save only first line from string?

On 10/03/2010 07:19 PM, Terry Michaels wrote:
> Hi. What's the most simple and elegant way to remove all the contents of
> a String except for the first line? (Assume string consist of one line,
> multiple lines, or no lines, and assume that we don't know which OS we
> are on.)
>    
Assuming you mean to actually modify the string, you could do this:

irb(main):001:0> "a string\nwith multiple\nlines".gsub! 
/\A(.*?)$(.*)\z/m, '\1'
=> "a string"
irb(main):002:0> "a string with one line".gsub! /\A(.*?)$(.*)\z/m, '\1'
=> "a string with one line"
irb(main):003:0> "".gsub! /\A(.*?)$(.*)\z/m, '\1'
=> ""

If you don't need to modify the string:

irb(main):004:0> "a string\nwith multiple\nlines".match(/\A.*?$/)[0]
=> "a string"
irb(main):005:0> "a string with one line".match(/\A.*?$/)[0]
=> "a string with one line"
irb(main):006:0> "".match(/\A.*?$/)[0]
=> ""


-Justin