Originální popis anglicky:
strtoul, strtoull, strtouq - convert a string to an unsigned long integer
Návod, kniha: Linux Programmer's Manual
#include <stdlib.h>
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' 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 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,
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 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 variable
errno
to ERANGE. Precisely the same holds for
strtoull() (with ULLONG_MAX
instead of ULONG_MAX).
- EINVAL
- (not in C99) The given base contains an unsupported
value.
- ERANGE
- 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).
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
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().
strtoul() conforms to SVID 3, BSD 4.3, ISO 9899 (C99) and POSIX, and
strtoull() to ISO 9899 (C99) and POSIX 1003.1-2001.
atof(3),
atoi(3),
atol(3),
strtod(3),
strtol(3)
