How do I use POSIX character classes in Vim search patterns?

Explanation

Vim supports POSIX character classes inside bracket expressions, providing a portable and readable way to match categories of characters. These are especially useful when you need to match locale-aware character sets or want more readable patterns than raw ranges.

How it works

• [:digit:] — digits (0-9)
• [:upper:] — uppercase letters
• [:lower:] — lowercase letters
• [:alpha:] — alphabetic characters
• [:alnum:] — alphanumeric characters
• [:space:] — whitespace characters
• [:punct:] — punctuation characters
• [:xdigit:] — hexadecimal digits

They must appear inside [] brackets: [[:digit:]]

Example

Find characters that are either digits or uppercase:

/[[:digit:][:upper:]]\+

Text: Hello World 42 test ABC
Matches: H, W, 42, ABC

Tips

• Combine with negation: [^[:digit:]] matches any non-digit
• Mix with regular chars: [[:digit:]abc] matches digits or a, b, c
• [:print:] matches printable characters — useful for finding non-printable bytes
• Vim also has shorthand equivalents: \d for [:digit:], \a for [:alpha:]