ustrtol man page
ustrtol — Converts a string into an integer. Allegro game programming library.
long ustrtol(const char *s, char **endp, int base);
This function converts the initial part of `s' to a signed integer, setting `*endp' to point to the first unused character, if `endp' is not a NULL pointer. The `base' argument indicates what base the digits (or letters) should be treated as. If `base' is zero, the base is determined by looking for `0x', `0X', or `0' as the first part of the string, and sets the base used to 16, 16, or 8 if it finds one. The default base is 10 if none of those prefixes are found. Example:
char *endp, *string = "456.203 askdfg"; int number = ustrtol(string, &endp, 10);
Returns the string converted as a value of type `long int'. If nothing was converted, returns zero with `*endp' pointing to the beginning of `s'.
uconvert(3), ustrtod(3), uatof(3)