|STRTOUL(3)||Linux Programmer's Manual||STRTOUL(3)|
unsigned long strtoul(const char *restrict nptr, char **restrict endptr, int base); unsigned long long strtoull(const char *restrict nptr, char **restrict endptr, int base);
_ISOC99_SOURCE || /* Glibc <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE
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 an unsigned 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 uppercase or lowercase 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 (and returns 0). In particular, if *nptr is not '\0' but **endptr is '\0' on return, the entire string is valid.
The strtoull() function works just like the strtoul() function but returns an unsigned long long value.
- (not in C99) The given base contains an unsupported value.
- The resulting value was out of range.
The implementation may also set errno to EINVAL in case no conversion was performed (no digits seen, and 0 returned).
|strtoul (), strtoull (), strtouq ()||Thread safety||MT-Safe locale|
strtoull(): POSIX.1-2001, POSIX.1-2008, C99.
In locales other than the "C" locale, other strings may be accepted. (For example, the thousands separator of the current locale may be supported.)
BSD also has
u_quad_t strtouq(const char *nptr, char **endptr, int base);
with completely analogous definition. Depending on the wordsize of the current architecture, this may be equivalent to strtoull() or to strtoul().
Negative values are considered valid input and are silently converted to the equivalent unsigned long value.