Regular Expressions 101

Pro

1st Alternative\b(?:field[1234])=\S+\b(?=.*\btype=a\b)

\ba Unicode word boundary

Non-Capturing Group(?:field[1234])

fieldthe literal text field (case sensitive)

Character Class[1234]

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

3the literal 3 (51₁₀ / 63₈ / 33₁₆)

4the literal 4 (52₁₀ / 64₈ / 34₁₆)

=the literal = (61₁₀ / 75₈ / 3D₁₆)

\S+any character that is not Unicode whitespace, repeated at least once

\ba Unicode word boundary

Positive Lookahead(?=.*\btype=a\b)

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

\ba Unicode word boundary

type=athe literal text type=a (case sensitive)

\ba Unicode word boundary

2nd Alternative (?<=\btype=a\b.*)\b(?:field[1234])=\S+\b

Positive Lookbehind(?<=\btype=a\b.*)

\ba Unicode word boundary

type=athe literal text type=a (case sensitive)

\ba Unicode word boundary

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

\ba Unicode word boundary

Non-Capturing Group(?:field[1234])

fieldthe literal text field (case sensitive)

Character Class[1234]

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

3the literal 3 (51₁₀ / 63₈ / 33₁₆)

4the literal 4 (52₁₀ / 64₈ / 34₁₆)

=the literal = (61₁₀ / 75₈ / 3D₁₆)

\S+any character that is not Unicode whitespace, repeated at least once

\ba Unicode word boundary

Global pattern flags

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

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

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

Detailed match information will be displayed here automatically.

25 tokens

\b(?:field[1234])=\S+\b(?=.*\btype=a\b)
|
(?<=\btype=a\b.*)\b(?:field[1234])=\S+\b

New

field1=foo this=garbage field2=bar type=a field3=now
field1=foo field2=bar type=b field3=now
field1=bar type=a field3=foo this=garbage field4=hithere

field1=foo this=garbage field2=bar type=a field3=now
field1=foo field2=bar type=b field3=now
field1=bar type=a field3=foo this=garbage field4=hithere