The
strtoul()
function
converts the string in
nptr
to an
unsigned long
value.
The
strtoull()
function
converts the string in
nptr
to an
unsigned long long
value.
The
strtoumax()
function
converts the string in
nptr
to an
uintmax_t
value.
The
strtouq()
function
converts the string in
nptr
to a
u_quad_t
value.
The conversion is done 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(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 not
NULL,
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
‘\0’
but
**endptr
is
‘\0’
on return, the entire string was valid.)
