正则表达式 - 在某些字符之后匹配文本

Question

I want to scrape data from some text and dump it into an array. Consider the following text as example data:

| Example Data
| Title: This is a sample title
| Content: This is sample content
| Date: 12/21/2012

I am currently using the following regex to scrape the data that is specified after the 'colon' character:

/((?=:).+)/

Unfortunately this regex also grabs the colon and the space after the colon. How do I only grab the data?

Also, I'm not sure if I'm doing this right.. but it appears as though the outside parens causes a match to return an array. Is this the function of the parens?

EDIT: I'm using Rubular to test out my regex expressions

Answer 1

You could change it to:

/: (.+)/

and grab the contents of group 1. A lookbehind works too, though, and does just what you're asking:

/(?<=: ).+/

Answer 2

In addition to @minitech's answer, you can also make a 3rd variation:

/(?<=: ?)(.+)/

The difference here being, you create/grab the group using a look-behind.

If you still prefer the look-ahead rather than look-behind concept. . .

/(?=: ?(.+))/

This will place a grouping around your existing regex where it will catch it within a group.

And yes, the outside parenthesis in your code will make a match. Compare that to the latter example I gave where the entire look-ahead is 'grouped' rather than needlessly using a /( ... )/ without the /(?= ... )/ , since the first result in most regular expression engines return the entire matched string.

Answer 3

I know you are asking for regex but I just saw the regex solution and found that it is rather hard to read for those unfamiliar with regex.

I'm also using Ruby and I decided to do it with:

line_as_string.split(": ")[-1]

This does what you require and IMHO it's far more readable. For a very long string it might be inefficient. But not for this purpose.

Answer 4

In Ruby, as in PCRE and Boost, you may make use of the \\K match reset operator :

\\K keeps the text matched so far out of the overall regex match. h\\Kd matches only the second d in adhd .

So, you may use

/:[[:blank:]]*\K.+/     # To only match horizontal whitespaces with `[[:blank:]]`
/:\s*\K.+/              # To match any whitespace with `\s`

Seee the Rubular demo #1 and the Rubular demo #2 and

Details

• : - a colon
• [[:blank:]]* - 0 or more horizontal whitespace chars
• \\K - match reset operator discarding the text matched so far from the overall match memory buffer
• .+ - matches and consumes any 1 or more chars other than line break chars (use /m modifier to match any chars including line break chars).