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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’ pre‐
fix, 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, str
toul() 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 vari‐
able 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.