Regular Expressions 101

Explanation
Pro

^start of line

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

Group 1([^#]\S+?)

Negated Character Class[^#]

#the literal # (35₁₀ / 43₈ / 23₁₆)

\S+?any non-whitespace character, repeated at least once

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

=the literal = (61₁₀ / 75₈ / 3D₁₆)

Group 2(.*)

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

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.

25 tokens

^\s*([^#]\S+?)\s*=(.*)

New

key=
key=value
key =value
key = value
key	=	value
key	=	value with whitespaces

key=
key=value
key =value
key = value
key	=	value
key	=	value with whitespaces