Pointers to Pointers: What datatype with variable length strings?

If you have a collection of unsigned char * values:

unsigned char *name_0 = "Joseph";
unsigned char *name_1 = "Helen";
unsigned char *name_2 = "Maximillian";

Then you can create:

unsigned char *data[] = { name_0, name_1, name_2 };
unsigned char **listOfNames = data;

Note that you need to allocate space for the list of pointers — in my code, that's the data array. You could use malloc() instead, but you'd need to remember to code the matching free() at some point.

Adding appropriate const qualifications is left as an exercise in frustration to the interested reader.

If you are reading a variable length list of names from a file a run time, with (presumably) one name per line, then you'd do best with POSIX getline() and strdup().

There must be a number of other questions that deal with this scenario, so I'll be terse with this code:

char **read_file(FILE *fp)
{
    char  *buffer = 0;
    size_t bufsiz = 0;
    char **lines = 0;
    size_t n_lines = 0;
    size_t n_alloc = 0;

    while (getline(&buffer, &bufsiz, fp) > 0)
    {
        if (n_lines + 1 >= n_alloc)
        {
            size_t new_num = (n_alloc + 1) * 2;
            size_t new_size = new_num * sizeof(*lines);
            char **new_lines = realloc(lines, new_size);
            if (new_lines == 0)
            {
                free(buffer);
                free(lines);
                return(0);
            }
            lines = new_lines;
            n_alloc = new_num;
        }
        lines[n_lines++] = strdup(buffer);  // Includes newline!
    }
    lines[n_lines] = 0;  // Null terminate list of strings
    free(buffer);        // Release input line's memory
    return lines;
}

Note that the code uses plain char and not unsigned char. You face some issues if you use unsigned char because neither getline() nor strdup() expects to work with unsigned char. While you can cast your way around the issue, it is messy to do so.