Regular Expressions 101

^start of line

Group 1((?:\d+\.?){4})

Non-Capturing Group(?:\d+\.?){4}

{4}repeats the group contents below exactly 4 times:

\d+a digit, repeated at least once

\.?optionally matches the literal . (46₁₀ / 56₈ / 2E₁₆)

Non-Capturing Group(?:.+?"){4}

{4}repeats the group contents below exactly 4 times:

.+?any character (except for line terminators), repeated at least once

"the literal " (34₁₀ / 42₈ / 22₁₆)

\s+any whitespace character, repeated at least once

Group 2(".*?")

"the literal " (34₁₀ / 42₈ / 22₁₆)

.*?any character (except for line terminators), repeated any number of times

"the literal " (34₁₀ / 42₈ / 22₁₆)

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

^((?:\d+\.?){4})(?:.+?"){4}\s+(".*?")

Test String
New

66.249.74.18 - - [21/Apr/2013:05:55:33 +0000] 200 "GET /1.jpg HTTP/1.1" 7691 "-" "Googlebot-Image/1.0" "-"
220.181.108.96 - - [21/Apr/2013:05:55:33 +0000] 200 "GET /1.html HTTP/1.1" 17722 "-" "Mozilla/5.0 (compatible; Baiduspider/2.0; +http://www.baidu.com/search/spider.html)" "-"

Regular Expression

Test StringNew

SubstitutionProcessing...

Test String
New

Substitution
Processing...