Regular Expressions 101

Pro

^start of line

Positive Lookahead(?=.{0,25}$)

.{0,25}any character (except for line terminators), repeated between 0 and 25 times

$end of line

Character Class[+#]?

?matches at most one character from the set below:

+the literal + (43₁₀ / 53₈ / 2B₁₆)

#the literal # (35₁₀ / 43₈ / 23₁₆)

\d*a digit, repeated any number of times

Non-Capturing Group(?:X*|\*?)

1st AlternativeX*

X*the literal X (88₁₀ / 130₈ / 58₁₆) (case sensitive), repeated any number of times

2nd Alternative\*?

\*?optionally matches the literal * (42₁₀ / 52₈ / 2A₁₆)

$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

Regular Expression

^(?=.{0,25}$)[+#]?\d*(?:X*|\*?)$

New

The regex should match any given number:

012345
+12345
#1234525
But also match for strings with a X in it.

12345X
12345XX
1234XXXXXX
XXXXXX

also
12345*

Not allowed
1234*X
1234X*
1234**
1234X*
12345*X

Substitution

The regex should match any given number:

012345
+12345
#1234525
But also match for strings with a X in it.

12345X
12345XX
1234XXXXXX
XXXXXX

also
12345*

Not allowed
1234*X
1234X*
1234**
1234X*
12345*X