Regular Expressions 101

^start of line

Character Class[0-9]{0,3}

{0,3}matches between 0 and 3 characters from the set below:

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

Positive Lookahead(?=-)

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Character Class[0-9-]{0,4}

{0,4}matches between 0 and 4 characters from the set below:

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

-the literal - (45₁₀ / 55₈ / 2D₁₆)

$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.

Search reference

Regular Expression

^[0-9]{0,3}(?=-)[0-9-]{0,4}$

New

123-123