How to use regular expressions in C?
You can use PCRE:
The PCRE library is a set of functions that implement regular expression pattern matching using the same syntax and semantics as Perl 5. PCRE has its own native API, as well as a set of wrapper functions that correspond to the POSIX regular expression API. The PCRE library is free, even for building commercial software.
See pcredemo.c for a PCRE example.
If you cannot use PCRE, POSIX regular expression support is probably available on your system (as @tinkertim pointed out). For Windows, you can use the gnuwin Regex for Windows package.
The regcomp
documentation includes the following example:
#include <regex.h>
/*
* Match string against the extended regular expression in
* pattern, treating errors as no match.
*
* Return 1 for match, 0 for no match.
*/
int
match(const char *string, char *pattern)
{
int status;
regex_t re;
if (regcomp(&re, pattern, REG_EXTENDED|REG_NOSUB) != 0) {
return(0); /* Report error. */
}
status = regexec(&re, string, (size_t) 0, NULL, 0);
regfree(&re);
if (status != 0) {
return(0); /* Report error. */
}
return(1);
}
If forced into POSIX only (no pcre), here's a tidbit of fall back:
#include <regex.h>
#include <stdbool.h>
bool reg_matches(const char *str, const char *pattern)
{
regex_t re;
int ret;
if (regcomp(&re, pattern, REG_EXTENDED) != 0)
return false;
ret = regexec(&re, str, (size_t) 0, NULL, 0);
regfree(&re);
if (ret == 0)
return true;
return false;
}
You might call it like this:
int main(void)
{
static const char *pattern = "/foo/[0-9]+$";
/* Going to return 1 always, since pattern wants the last part of the
* path to be an unsigned integer */
if (! reg_matches("/foo/abc", pattern))
return 1;
return 0;
}
I highly recommend making use of PCRE if its available. But, its nice to check for it and have some sort of fall back.
I pulled the snippets from a project currently in my editor. Its just a very basic example, but gives you types and functions to look up should you need them. This answer more or less augments Sinan's answer.