STRTOUL(3) Linux Programmer's Manual STRTOUL(3)
strtoul, strtoull, strtouq - convert a string to an unsigned long inte-
unsigned long int
strtoul(const char *nptr, char **endptr, int base);
unsigned long long int
strtoull(const char *nptr, char **endptr, int base);
The strtoul() function converts the initial part of 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 (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 integer value.
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. Precisely the same holds for strtoull() (with
ULLONG_MAX instead of ULONG_MAX).
ERANGE The resulting value was out of range.
EINVAL (not in C99) The given base contains an unsupported value.
The implementation may also set errno to EINVAL in case no conversion
was performed (no digits seen, and 0 returned).
In locales other than the "C" locale, also other strings may be
accepted. (For example, the thousands separator of the current locale
may be supported.)
BSD also has
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 str-
strtoul() conforms to SVID 3, BSD 4.3, ISO 9899 (C99) and POSIX, and
strtoull() to ISO 9899 (C99) and POSIX-2001.
atof(3), atoi(3), atol(3), strtod(3), strtol(3)
GNU 2002-05-30 STRTOUL(3)