CODEWITHSUNDEEP
regexpcreregex-greedy
l0_0
l0_0

Reputation: 43

A multi-line, variedly greedy, regular expression

Given the following text, what PCRE regular expression would you use to extract the parts marked in bold?

00:20314 lorem ipsum
  want this
  kryptonite

00:02314 quux
  padding
  dont want this

00:03124 foo
     neither this

00:01324 foo
     but we want this
     stalagmite

00:02134 tralala
     not this

00:03124 bar foo
     and we want this
     kryptonite but not this(!)

00:02134 foo bar
     and not this either

00:01234 dolor sit amet
     EOF

IOW, we want to extract sections that start, in regex terms, with "^0" and end with "(kryptonite|stalagmite)".

Been chomping on this for a bit, finding it a hard nut to crack. TIA!

Upvotes: 4

Views: 1918

Answers (4)

hwnd
hwnd

Reputation: 70732

One way to do this would be Negative Lookahead combined with inline (?sm) dotall and multi-line modifiers.

(?sm)^0(?:(?!^0).)*?(?:kryptonite|stalagmite)

Live Demo

Upvotes: 4

Sam
Sam

Reputation: 20486

I believe this will be the most efficient:

^0(?:\R(?!\R)|.)*?\b(?:kryptonite|stalagmite)\b

Demo

Obviously we start with ^0 and then end with either kryptonite or stalagmite (in a non-capturing group, for the heck of it) surrounded by \b word boundaries.

(?:\R(?!\R)|.)*? is the interesting part though, so let's break it down. One key concept first is PCRE's \R newline sequence.

(?:      (?# start non-capturing group for repetition)
  \R     (?# match a newline character)
  (?!\R) (?# not followed by another newline)
 |       (?# OR)
  .      (?# match any character, except newline)
)*?      (?# lazily repeat this group)

Upvotes: 2

user557597
user557597

Reputation:

This looks like it works. 

 # (?ms)^0(?:(?!(?:^0|kryptonite|stalagmite)).)*(kryptonite|stalagmite)

 (?ms)
 ^ 0
 (?:
      (?!
           (?: ^ 0 | kryptonite | stalagmite )
      )
      . 
 )*
 ( kryptonite | stalagmite )

Upvotes: 3

atxdba
atxdba

Reputation: 5216

^(00:.*?(kryptonite|stalagmite)) with the s modifier

Upvotes: -1

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