CODEWITHSUNDEEP
regexpcre
kahsay kalayu
kahsay kalayu

Reputation: 309

pcre_regex with conditional patterns, "or" and "and" conditions

Am using a pcre-regex-engine to match pattern from my file/line. The lines am trying to find a match are:

line-001 key_one:10.20.30.40 any data goes here
line-002 key_two:11.22.33.44 any data goes here
line-003 key_off:12.32.42.52 any data goes here
line-004 key_ten:34.45.67.89 any data goes here

Now, I want to match ip patterns starting with key_one:,key_two: orkey_ten:. I need my pattern to be conditional,"match any ip pattern starting with key_one:or,key_two: or key_ten:.

expected pattern= key_one | key_two| key_ten & (\d+.\d+.\d+.\d+)

But, The or(|) condition works for pcre,but not the and(&) condition. can some one help me out to use the and (&) condition? thank u.

Upvotes: 1

Views: 1046

Answers (1)

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 626870

Your regex is almost correct: you did not consider that the spaces in the pattern are meaningful (in PCRE, outside the character classes) unless /x modifier is used, and that there is a colon between the values. Also, a dot must be escaped to match a literal dot.

You may use

(key_(?:one|two|ten)):(\d{1,3}(?:\.\d{1,3}){3})

that is a contracted form of

(key_one|key_two|key_ten):(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})

See the regex demo

If you need to get the IP as a match value, use \K operator to discard all the text matched up to that operator and return only what is matched later:

key_(?:one|two|ten):\K\d{1,3}(?:\.\d{1,3}){3}

See this regex demo.

Note that it is best practice to write the alternatives in such a way that none of them could match at the same location (to improve performance), that is why it is not a good idea to repeat the same key_ substring within the (...|...).

The + quantifier matches 1 or more occurrences and in IP addresses there can only be one to three digits, that is why a limiting quantifier {1,3} seems more reliable.

Also, to avoid unnecessary captures, just turn capturing ((...)) groups into non-capturing ones ((?:...)).

Upvotes: 1

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