long strtol(const char *str, char **endptr, int base);
strtol() function converts the string in
str to a long value. The conversion is done according to the given base, which must be between 2 and 16 inclusive, or be the special value 0.
The string may begin with an arbitrary amount of white space (as determined by
isspace()) followed by a single optional
+' or-' sign. If base is zero or 16, the string may then include a
0x' prefix, and the number will be read in base 16; otherwise, a zero base is taken as 10 (decimal) unless the next character is `0', in which case it is taken as 8 (octal).
The remainder of the string is converted to a long in the obvious manner, stopping at the first character which is not a valid digit in the given base. (In bases above 10, the letter
A' in either upper or lower case represents 10,B' represents 11, and so forth, with `Z' representing 35.)
endptr is not
strtol() stores the address of the first invalid character in
*endptr. If there were no digits at all, however,
strtol() stores the original value of str in
*endptr. (Thus, if
*str is not
\0 on return, the entire string was valid.)