CODEWITHSUNDEEP
cregex
Fish-Guts
Fish-Guts

Reputation: 336

Regex doesn't work as expected

I am trying to match a valid nickname in C.

I have the following function: 

int check_valid_nickname(char *nick) {
    if(!match(nick,NICK_PATTERN)) {
        return 0;
    } else {
}

int match(char *str, char *pattern) {
    int    status;
    regex_t re;
    if (regcomp(&re, pattern, REG_EXTENDED|REG_NOSUB) != 0) {
        /* Report error. */
        return 0;
    }
    status = regexec(&re, str, (size_t) 0, NULL, 0);
    regfree(&re);
    if (status != 0) {
        /* Report error. */
        return 0;
    }
    return 1;
}

and NICK_PATTERN is defined as 

#define NICK_PATTERN "/^[a-z0-9_\\|\\{\\}\\[\\]\\^]{4,36}$/i"

I have tested the pattern on regexr and it matches perfectly the way I need it.

However, my function in C is still always returning 0. Am I overlooking something? Thanks for any pointers.

Upvotes: 0

Views: 316

Answers (1)

Wintermute
Wintermute

Reputation: 44063

The regex you're looking for is

#define NICK_PATTERN "^[]a-z0-9|{}^[]{4,36}$"

and you want to compile it like so:

regcomp(&re, pattern, REG_ICASE | REG_EXTENDED | REG_NOSUB)

regcomp, regexec etc. use the POSIX regular expression syntax, which means slightly different escaping rules, no slashes for matching, and no flags like in Perl -- these are replaced, in a manner of speaking, by the functions and their flags. There's a rundown of POSIX syntax here. It is written for a C++ interface, but the rules are the same.

Differences from what you expected in this particular case: You don't have to escape in a [] set, and if there's a ] to be part of the set, it has to come at the front.

Upvotes: 1

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