Regular Expressions 101

Pro

^start of line

Non-Capturing Group(?:'(?=.*')|(?=[^']+$))

1st Alternative'(?=.*')

'the literal ' (39₁₀ / 47₈ / 27₁₆)

Positive Lookahead(?=.*')

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

'the literal ' (39₁₀ / 47₈ / 27₁₆)

2nd Alternative(?=[^']+$)

Positive Lookahead(?=[^']+$)

Negated Character Class[^']+

+matches at least one character outside the set below:

'the literal ' (39₁₀ / 47₈ / 27₁₆)

$end of line

Character Class[a-z]

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

'?optionally matches the literal ' (39₁₀ / 47₈ / 27₁₆)

$end of line

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

^(?:'(?=.*')|(?=[^']+$))[a-z]'?$

New

hello
one letter below
a
another letter below, but signle quoted
'a'

a'

'a

hello
one letter below
a
another letter below, but signle quoted
'a'

a'

'a