Regular Expressions 101

Explanation

Pro

^start of line

Character Class[a-zA-Z]

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

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

Character Class[a-zA-Z0-9]*

*matches any number of characters from the set below:

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

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

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

Non-Capturing Group(?:[ _\-][a-zA-Z0-9]+)*

*repeats the group contents below any number of times:

Character Class[ _\-]

the literal (32₁₀ / 40₈ / 20₁₆)

_the literal _ (95₁₀ / 137₈ / 5F₁₆)

\-the literal - (45₁₀ / 55₈ / 2D₁₆)

Character Class[a-zA-Z0-9]+

+matches at least one character from the set below:

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

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

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

$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.

27 tokens

^[a-zA-Z][a-zA-Z0-9]*(?:[ _\-][a-zA-Z0-9]+)*$

New

Valid:

a_B
a_b
a b
a B
a_btest_psom
a-B
a43 b
a43_c
Invalid:

a_
_a
a-
a_b_
a_B_
a_b-
a_btest_psom_
43 b
43_c
434343