unsigned
long
int
strtoul(
const char * restrict nptr
, char ** restrict endptr
, int base
)
unsigned
long
long
int
strtoull(
const char * restrict nptr
, char ** restrict endptr
, int base
)
uintmax_t
strtoumax(const char * restrict nptr
, char ** restrict endptr
, int base
)
u_quad_t
strtouq(const char * restrict nptr
, char ** restrict endptr
, int base
)
)
function
converts the string in
nptr
to an
unsigned long int
value.
The
strtoull(
)
function
converts the string in
nptr
to an
unsigned long long int
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 non nil,
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.)
)
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
,
strtoull(
)
returns
ULLONG_MAX
,
strtoumax(
)
returns
UINTMAX_MAX
,
and the global variable
errno
is set to
ERANGE
.
There is no way to determine if
strtoul()
has processed a negative number (and returned an unsigned value) short of
examining the string in
nptr
directly.
If no error occurs, errno is left unchanged. This behavior (which is unlike most library functions) is guaranteed by the pertinent standards.
)
cannot be used unambiguously to detect an error,
errno
is left unchanged after a successful call.
To ensure that a string is a valid number (i.e., in range and containing no
trailing characters), clear
errno
beforehand explicitly, then check it afterwards:
char *ep;
unsigned long ulval;
...
errno = 0;
ulval = strtoul(buf, &ep, 10);
if (buf[0] == '\0' || *ep != '\0')
goto not_a_number;
if (errno == ERANGE && ulval == ULONG_MAX)
goto out_of_range;
This example will accept ``12'' but not ``12foo'' or ``12\n''. If trailing whitespace is acceptable, further checks must be done on *ep; alternately, use sscanf(3).
ERANGE
]
)
function
conforms to
ANSI X3.159-1989 (``ANSI C89'') .
The
strtoull(
)
and
strtoumax(
)
functions conform to
ISO/IEC 9899:1999 (``ISO C99'') .