C regex get all matches

regExMatches.c

#include <stdio.h>
#include <string.h>
#include <regex.h>

#define TEST_REGEX          "^.*\\/([a-zA-Z_.]*)\\.log : [A-Z]{3} [0-9]{2}\\/[0-9]{2} [0-9]{2}:[0-9]{2}:[0-9]{2}\\.[0-9]{6} .* : (.*)$"
#define MAX_REGEX_MATCHES   5
#define MAX_STRING_SIZE     1000
#define MAX_ERR_LENGTH      50

/**
 * Test regex against string. Requires 2D char array large enough to store found matches.
 * 
 * @param source 
 * @param pattern 
 * @param matches 
 * @return int - Number of matches found
 */
int getRegExMatches(char *source, const char *pattern, char matches[][MAX_STRING_SIZE]) {

    int err = 0, numMatches = 0, numGroups = 0;
    char errMsg[MAX_ERR_LENGTH];
    regex_t myRegEx;

    if ((err = regcomp(&myRegEx, pattern, REG_EXTENDED)) != 0) {
        regerror(err, &myRegEx, errMsg, MAX_ERR_LENGTH);
        printf("Error compiling regular expression '%s': %s", pattern, errMsg);
        return 0;
    }
    
    // re_nsub contains number of groups (possible matches) in the compiled regex
    // the first element of the array (index 0) contains the string that matched the entire 
    // regular expression, then comes the matching groups, so we must +1 to account for this
    numGroups = myRegEx.re_nsub + 1;
    regmatch_t rm[numGroups];

    // if there are matches:
    //              rm[0] = full match (this will be discarded)
    //              rm[1] = group 1 match
    //              rm[2] = group 2 match, etc...
    if ((err = regexec(&myRegEx, source, numGroups, rm, 0)) == 0) {
        for (unsigned int i = 1; i <= myRegEx.re_nsub; i++) {
			
            if (rm[i].rm_so == -1) {
                break; // no more matches
            }
            
            int len = rm[i].rm_eo - rm[i].rm_so;
            memcpy(matches[i-1], (source + rm[i].rm_so), len);
            matches[i-1][len] = '\0';
            
            printf("Match %u: [%s]\n", i, matches[i-1]);
            
            numMatches++;
        }

    } else if (err != REG_NOMATCH) {
        regerror(err, &myRegEx, errMsg, MAX_ERR_LENGTH);
        printf("Error executing regular expression '%s': %s", pattern, errMsg);
        regfree(&myRegEx);
        return 0;
    }

    regfree(&myRegEx);

    return numMatches;
}

int main() {

    char matches[MAX_REGEX_MATCHES][MAX_STRING_SIZE];
    char testSource[MAX_STRING_SIZE];

    strcpy(testSource, "/var/log/myTestApp.log : ERR 02/18 17:05:14.872780 matt : This is an important log entry.");

    getRegExMatches(testSource, TEST_REGEX, matches);

    return 0;
}