Regular Expressions 101

Explanation

Pro

^start of line

Group time(?<time>[^ +][-:0-9TZ]+|[[:upper:]][[:lower:]]{2}[ -:+0-9TZ]*)

1st Alternative[^ +][-:0-9TZ]+

Negated Character Class[^ +]

the literal (32₁₀ / 40₈ / 20₁₆)

+the literal + (43₁₀ / 53₈ / 2B₁₆)

Character Class[-:0-9TZ]+

+matches at least one character from the set below:

-the literal - (45₁₀ / 55₈ / 2D₁₆)

:the literal : (58₁₀ / 72₈ / 3A₁₆)

0-9one character from 0 (48₁₀) to 9 (57₁₀)

Tthe literal T (84₁₀ / 124₈ / 54₁₆) (case sensitive)

Zthe literal Z (90₁₀ / 132₈ / 5A₁₆) (case sensitive)

2nd Alternative[[:upper:]][[:lower:]]{2}[ -:+0-9TZ]*

Character Class[[:upper:]]

[:upper:]an uppercase letter [A-Z]

Character Class[[:lower:]]{2}

{2}matches exactly 2 characters from the set below:

[:lower:]a lowercase letter [a-z]

Character Class[ -:+0-9TZ]*

*matches any number of characters from the set below:

-:one character from (32₁₀) to : (58₁₀)

+the literal + (43₁₀ / 53₈ / 2B₁₆)

0-9one character from 0 (48₁₀) to 9 (57₁₀)

Tthe literal T (84₁₀ / 124₈ / 54₁₆) (case sensitive)

Zthe literal Z (90₁₀ / 132₈ / 5A₁₆) (case sensitive)

Group 2([^ ][+0:]+|\s+)

1st Alternative[^ ][+0:]+

Negated Character Class[^ ]

the literal (32₁₀ / 40₈ / 20₁₆)

Character Class[+0:]+

+matches at least one character from the set below:

+the literal + (43₁₀ / 53₈ / 2B₁₆)

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

:the literal : (58₁₀ / 72₈ / 3A₁₆)

2nd Alternative\s+

\s+any whitespace character, repeated at least once

Group 3(\s*)

\s*any whitespace character, repeated any number of times

Group host(?<host>[^ ][-\w\d]+)

Negated Character Class[^ ]

the literal (32₁₀ / 40₈ / 20₁₆)

Character Class[-\w\d]+

+matches at least one character from the set below:

-the literal - (45₁₀ / 55₈ / 2D₁₆)

\wany word character

\da digit

Group 5(\s*)

\s*any whitespace character, repeated any number of times

Group service(?<service>[^ [][-_\w]+)

Negated Character Class[^ []

the literal (32₁₀ / 40₈ / 20₁₆)

[the literal [ (91₁₀ / 133₈ / 5B₁₆)

Character Class[-_\w]+

+matches at least one character from the set below:

-the literal - (45₁₀ / 55₈ / 2D₁₆)

_the literal _ (95₁₀ / 137₈ / 5F₁₆)

\wany word character

Group 7(\[(?<pid>[^ \]][\d]*)\])

\[the literal [ (91₁₀ / 133₈ / 5B₁₆)

Group pid(?<pid>[^ \]][\d]*)

Negated Character Class[^ \]]

the literal (32₁₀ / 40₈ / 20₁₆)

\]the literal ] (93₁₀ / 135₈ / 5D₁₆)

Character Class[\d]*

*matches any number of characters from the set below:

\da digit

\]the literal ] (93₁₀ / 135₈ / 5D₁₆)

:the literal : (58₁₀ / 72₈ / 3A₁₆)

\s*any whitespace character, repeated any number of times

Group 9((\[\s*(?<mtime>[^ ][\w: \/]+)\]\s*\[\s*(?<severity>[^ ][\w]+)\]\s*){0,1}\s*\[\s*(?<component>[^ ][\w:]+)\]){0,1}

\s*any whitespace character, repeated any number of times

Group message(?<message>.*){0,1}

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

$end of line

Global pattern flags

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

x modifier: extended. Ignores unescaped whitespace and comments outside character classes

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

Unit Test Summary

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Quick Reference

25 tokens

Regular Expression

^(?<time>[^ +][-:0-9TZ]+|[[:upper:]][[:lower:]]{2}[ -:+0-9TZ]*)([^ ][+0:]+|\s+)(\s*)(?<host>[^ ][-\w\d]+)(\s*)(?<service>[^ [][-_\w]+)(\[(?<pid>[^ \]][\d]*)\]):\s*((\[\s*(?<mtime>[^ ][\w: \/]+)\]\s*\[\s*(?<severity>[^ ][\w]+)\]\s*){0,1}\s*\[\s*(?<component>[^ ][\w:]+)\]){0,1}\s*(?<message>.*){0,1}.*$

Unit Tests

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