How can I extract an integer from within a string?

strtol doesn't find a number in a string. It converts the number at the beginning of the string. (It does skip whitespace, but nothing else.)

If you need to find where a number starts, you can use something like:

const char* nump = strpbrk(str, "0123456789");
if (nump == NULL) /* No number, handle error*/

(man strpbrk)

If your numbers might be signed, you'll need something a bit more sophisticated. One way is to do the above and then back up one character if the previous character is -. But watch out for the beginning of the string:

if ( nump != str && nump[-1] == '-') --nump;

Just putting - into the strpbrk argument would produce false matches on input like non-numeric7.

If the format is always like this, then this could also work

#include <stdio.h>

int main()
{
    char *str[] = {"a5 d8", "fe55 eec2", "a5 abc111"};
    int num1, num2;

    for (int i = 0; i < 3; i++) {
      sscanf(str[i], "%*[^0-9]%d%*[^0-9]%d", &num1, &num2);
      printf("num1: %d, num2: %d\n", num1, num2);
    }
    return 0;
}

Output

num1: 5, num2: 8                                                                                                                                                                   
num1: 55, num2: 2                                                                                                                                                                  
num1: 5, num2: 111

%[^0-9] will match any non digit character. By adding the * like this %*[^0-9] indicates that the data is to be read from the string, but ignored.