#include <stdio.h>
#include <regex.h>
 
int match(const char *string, const char *pattern) {
    regex_t re;
 
    if (regcomp(&re, pattern, REG_EXTENDED|REG_NOSUB) != 0) {
        return 0;
    }
    int status = regexec(&re, string, 0, NULL, 0);
    regfree(&re);
    if (status != 0) {
        return 0;
    }
 
    return 1;
}
 
int main(void) {
    const char *reg = "^[a-zA-Z0-9_-]+\\.csv$";
    if (!match("test.csv", reg)) {
        printf("Not a valid csv file.\n");
    } else {
        printf("Valid csv file.\n");
    }
 
    return 0;
}

I2luY2x1ZGUgPHN0ZGlvLmg+CiNpbmNsdWRlIDxyZWdleC5oPgoKaW50IG1hdGNoKGNvbnN0IGNoYXIgKnN0cmluZywgY29uc3QgY2hhciAqcGF0dGVybikgewogICAgcmVnZXhfdCByZTsKCiAgICBpZiAocmVnY29tcCgmcmUsIHBhdHRlcm4sIFJFR19FWFRFTkRFRHxSRUdfTk9TVUIpICE9IDApIHsKICAgICAgICByZXR1cm4gMDsKICAgIH0KICAgIGludCBzdGF0dXMgPSByZWdleGVjKCZyZSwgc3RyaW5nLCAwLCBOVUxMLCAwKTsKICAgIHJlZ2ZyZWUoJnJlKTsKICAgIGlmIChzdGF0dXMgIT0gMCkgewogICAgICAgIHJldHVybiAwOwogICAgfQoKICAgIHJldHVybiAxOwp9CgppbnQgbWFpbih2b2lkKSB7CiAgICBjb25zdCBjaGFyICpyZWcgPSAiXlthLXpBLVowLTlfLV0rXFwuY3N2JCI7CiAgICBpZiAoIW1hdGNoKCJ0ZXN0LmNzdiIsIHJlZykpIHsKICAgICAgICBwcmludGYoIk5vdCBhIHZhbGlkIGNzdiBmaWxlLlxuIik7CiAgICB9IGVsc2UgewogICAgICAgIHByaW50ZigiVmFsaWQgY3N2IGZpbGUuXG4iKTsKICAgIH0KCiAgICByZXR1cm4gMDsKfQ==