`trex`

Description and usage

trex is a tiny regex library with UTF-8 support.

Usage is simple:

if (regexmatch("^\\\\fcharset\\d+ ?$", rtfcommand)) { 
    /* set the character set for the current font definition */ 
}

Public domain
UTF-8 aware and locale aware
Small source code size (< 100 SLOC)
Small binary size (~3.5kb on macOS, ~4kb on Linux)
No dynamic memory allocation
Supports standard metacharacter classes \d, \s, and \w
Easy to add additional metacharacter classes (e.g., supports \x for hexadecimal digits out of the box)

No character sets, e.g., [0-9]
No character groups or alternates, e.g., (abc|def)
No quantifiers, e.g., \d{1,5}
No support for index or match length (return value only indicates whether there's a match)
Locale support relies on system library iswxxxxx functions