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strtoul - convert a string to an unsigned long integer.
unsigned long int strtoul(const char *nptr, char **endptr,
The strtoul() function converts the string in nptr to an unsigned long
integer value according to the given base, which must be between 2 and
36 inclusive, or be the special value 0.
The string must 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 an unsigned long int 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 not NULL, strtoul() stores the address of the first
invalid character in *endptr. If there were no digits at all,
strtoul() stores the original value of nptr in *endptr. (Thus, if
*nptr is not `\0' but **endptr is `\0' on return, the entire string is
The strtoul() function 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 the global
variable errno to ERANGE.
ERANGE The given string was out of range; the value converted has been
SVID 3, BSD 4.3, ISO 9899
atof(3), atoi(3), atol(3), strtod(3), strtol(3)
Ignores the current locale.