The
strtol() function converts the string in
nptr to a
long int value. The
strtoll() function converts the string in
nptr to a
long long int value. The
strtoimax() function converts the string in
nptr to an
intmax_t value. The
strtoq() function converts the string in
nptr to a
quad_t value. The conversion is done according to the given
base, which must be between 2 and 36 inclusive, or be the special value 0.
The string may begin with an arbitrary amount of white space (as determined by
isspace(3)) 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 value 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.)
If
endptr is non-nil,
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
nptr in
*endptr. (Thus, if
*nptr is not ‘\0' but
**endptr is ‘\0' on return, the entire string was valid.)