C - Parsing Phone Number From String

Question

I am trying to extract a the phone numbers from the a file and print them out

Input

my number is (123) 456-7897 ok, my other number is (654) 393-3030 buddy.

My variables are

char *last_token;
char *firstpart;
char buffer[BUFFER_SIZE];
char *phoneNumber;

Here is my current loop

while( fgets(buffer, BUFFER_SIZE, input) != NULL ){
        last_token = strtok( buffer, " \n" );
        while(last_token != NULL) {
//see if first part of number is correct
            if(*last_token == '(' && isdigit(*(last_token + 1)) && isdigit(*(last_token + 2)) && isdigit(*(last_token + 3)) && *(last_token + 4) == ')' && *(last_token + 5) == '\0') {
                firstpart = last_token; //if it is save it
                last_token = strtok(NULL, " \n"); //check next part
//if second part is also correct
                if (isdigit(*last_token) && isdigit(*(last_token + 1)) && isdigit(*(last_token + 2)) && *(last_token + 3) == '-' && isdigit(*(last_token + 4)) && isdigit(*(last_token + 5)) && isdigit(*(last_token + 6)) && isdigit(*(last_token + 7)) && *(last_token + 8) == '\0') {
                    phoneNumber = firstpart; //set phone number to first part
                    strcat(phoneNumber, " "); //add a space to phone number
                    strcat(phoneNumber, last_token); //add the last part of the phone nmber

                    printf("%s\n", phoneNumber); //print the number
                }
            }
            last_token = strtok(NULL, " \n");
        }

}

It should be printing

(123) 456-7897
(654) 393-3030

But instead its printing

(123)
(654)

Im guessing that the string is getting terminated after the ) but I can't figure out why

Answer 1

strcat(phoneNumber, " ");

this was rewritten with '\0' to the beginning of the last_token.

char phoneNumber[15];
...
strcpy(phoneNumber, firstpart);
strcat(phoneNumber, " ");
strcat(phoneNumber, last_token);
printf("%s\n", phoneNumber);