Regular expression for a hexadecimal number?

Question

How do I create a regular expression that detects hexadecimal numbers in a text?

For example, ‘0x0f4’, ‘0acdadecf822eeff32aca5830e438cb54aa722e3’, and ‘8BADF00D’.

Answer 1

This one makes sure you have no more than three valid pairs:

(([a-fA-F]|[0-9]){2}){3}

Any more or less than three pairs of valid characters fail to match.

Answer 2

Another example: Hexadecimal values for css colors start with a pound sign, or hash (#), then six characters that can either be a numeral or a letter between A and F, inclusive.

^#[0-9a-fA-F]{6}

Answer 3

Not a big deal, but most regex engines support the POSIX character classes, and there's [:xdigit:] for matching hex characters, which is simpler than the common 0-9a-fA-F stuff.

So, the regex as requested (ie. with optional 0x) is: /(0x)?[[:xdigit:]]+/

Answer 4

If you're using Perl or PHP, you can replace

[0-9a-fA-F]

with:

[[:xdigit:]]

Answer 5

In case you need this within an input where the user can type 0 and 0x too but not a hex number without the 0x prefix:

^0?[xX]?[0-9a-fA-F]*$

Answer 6

If you are looking for an specific hex character in the middle of the string, you can use "\xhh" where hh is the character in hexadecimal. I've tried and it works. I use framework for C++ Qt but it can solve problems in other cases, depends on the flavor you need to use (php, javascript, python , golang, etc.).

This answer was taken from:http://ult-tex.net/info/perl/