Regular Expression Library :: Numbers
This page contains a collection of regular expressions for matching numbers in various formats. To match a string that matches one of these expressions as a whole rather than in part, put a ^ before the expression and a $ after it. For example, \d+ becomes ^\d+$.
Integer
Description: Matches any whole number, either positive or negative, allowing -0.
Perl Compatible Form: -?\d+
POSIX Form: -?[0-9]+
Integer With -0 Disallowed
Description: Matches any whole number, either positive or negative, not allowing -0.
Perl Compatible Form: -?0*[1-9]\d*|0+
POSIX Form: -?0*[1-9][0-9]*|0+
Integer With No Leading Zeroes
Description: Matches any whole number, either positive or negative, except when it has leading zeroes (that is, 4 and -2 will match, but 04 and -02 will not). -0 will match.
Perl Compatible Form: -?([1-9]\d*|0)
POSIX Form: -?([1-9][0-9]*|0)
Integer With No Leading Zeroes And -0 Disallowed
Description: Matches any whole number, either positive or negative, except when it has leading zeroes (that is, 4 and -2 will match, but 04 and -02 will not). -0 will not match.
Perl Compatible Form: -?[1-9]\d*|0
POSIX Form: -?([1-9][0-9]*|0)
Positive Integers
Description: A positive integer, excluding zero and with no leading zeroes allowed. Add |0 on the end to allow zero.
Perl Compatible Form: [1-9]\d*
POSIX Form: [1-9][0-9]*
Positive Integer Explicitly Rejecting Negatives
Description: A positive integer, excluding zero and with no leading zeroes allowed. Add |0 on the end to allow zero. This expression is useful when checking if a string contains a positive number and ignoring negatives. Note that the grouping (brackets) will count as a capture.
Perl Compatible Form: (^|[^-])[1-9]\d*
POSIX Form: (^|[^-])[1-9][0-9]*
Decimals
Description: Any decimal number. Remove the -? at the start to only allow positive decimals and change -? to - to only allow negative decimals.
Perl Compatible Form: -?\d+(\.\d+)?
POSIX Form: -?[0-9]+(\.[0-9]+)?
Number With Exponent
Description: Any decimal number with an optional decimal exponent. For example, 2.53e10 means the number 2.53 raised to the 10th power of ten (provided we are working in base 10)..
Perl Compatible Form: -?\d+(\.\d+)?(e\d+(\.\d+)?)?
POSIX Form: -?[0-9]+(\.[0-9]+)(e[0-9]+(\.[0-9]+)?)?
Binary (Base 2)
To match binary numbers, use the above expressions but re-write every instance of \d or [0-9] to be [01]. Any character class of the form [1-9] should be re-written written as 1.
Hex (Base 16)
To match hex numbers, use the above expressions but re-write every instance of \d or [0-9] to be [0-9A-F]. Any character class of the form [1-9] should be re-written as [1-9A-F].
Octal (Base 8)
To match octal numbers, use the above expressions but re-write every instance of \d or [0-9] to be [0-7]. Any character class of the form [1-9] should be re-written as [1-7].
