strtoul - convert a string to an unsigned long integer

#include <stdlib.h>
#include <limits.h>

unsigned long strtoul(const char *nptr, char **endptr, int base);

Strtoul converts the string in nptr to an unsigned long value
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; see ctype(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 an unsigned long value
in the obvious manner, stopping at the end of the string or at the
first character that does not produce 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, strtoul stores the address of the first
invalid character in *endptr. If there were no digits at all,
however, strtoul stores the original value of nptr in *endptr.
(Thus, if *nptr is not ’ ’ but **endptr is ’ ’ on return, the
entire string was valid.)

Strtoul returns either the result of the conversion or, if there
was a leading minus sign, the negation of the result of the
conversion, unless the original (non-negated) value would overflow;
in the latter case, strtoul returns ULONG_MAX and sets errno to

The given string was out of range; the value converted has
been clamped.


Strtoul conforms to ANSI X3.159-1989 ("ANSI C").

Ignores the current locale.