Regular Expressions 101

^start of line

Group 1(0|[1-9]\d*)

1st Alternative0

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

2nd Alternative[1-9]\d*

Character Class[1-9]

1-9one character from 1 (49₁₀) to 9 (57₁₀)

\d*a digit, repeated any number of times

$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|[1-9]\d*)$

New

3
999
-3
0
0.0
1.0
0.1
.01
-0.0000000000000000000000000000000001
2e3
-2e3
2e-3
-2e-3
1.0e0
0.1e1
.01e-1
-9.1e3
-9.1e-3
9E5
0e-11
0xff
0XFF
0x0
0xfe3
-0
-0.0
-0.0000000000000000000000000000000000
-.0
-.0000000000000000000000000000000000
1xff
0x
0x0fg3
0xf4.
.0xf
0xfe-3
-0xff
0.0xff
0xff.1
e89
.e3
001
-00.2
3.

a
 -1
--1
-.1
2..3
2-
2...3
2.4.3
5-6-7
.-1