Linux Programmer’s Manual
STRTOUL(3) Linux Programmer’s Manual STRTOUL(3)
NAME
strtoul, strtoull, strtouq - convert a string to an unsigned long integer
SYNOPSIS
#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);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
strtoull(): XOPEN_SOURCE >= 600 || _BSD_SOURCE || _SVID_SOURCE || _ISOC99_SOURCE; or cc -std=c99
DESCRIPTION
The strtoul() function converts the initial part of the string in nptr to an unsigned long int value 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 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 int value.
RETURN 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 represented as an unsigned value, unless the original (non-negated)
value would overflow; in the latter case, strtoul() returns ULONG_MAX and sets errno to ERANGE. Precisely the
same holds for strtoull() (with ULLONG_MAX instead of ULONG_MAX).
ERRORS
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).
CONFORMING TO
strtoul() conforms to SVr4, C89, C99 and POSIX-2001, and strtoull() to C99 and POSIX.1-2001.
NOTES
Since strtoul() can legitimately return 0 or ULONG_MAX (ULLONG_MAX for strtoull()) on both success and failure,
the calling program should set errno to 0 before the call, and then determine if an error occurred by checking
whether errno has a non-zero value after the call.
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 int
value.
EXAMPLE
See the example on the strtol(3) manual page; the use of the functions described in this manual page is simi-
lar.
SEE ALSO
atof(3), atoi(3), atol(3), strtod(3), strtol(3)
COLOPHON
This page is part of release 3.22 of the Linux man-pages project. A description of the project, and informa-
tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.
GNU 2007-07-26 STRTOUL(3)
http://blog.naver.com/websearch/220423721572
unsigned 64bit 숫자를 포함한 문자열을 uint64_t 로 변환하는 소스 코드 예제는 다음과 같습니다. 64 bit OS 에서는 두 개의 값이 동일하게 출력되고 32bit OS 에서는 다르게 출력된다.
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
int main( int argc, char * argv[] )
{
uint64_t iValue = strtoul( "18446744073709551615", NULL, 10 );
uint64_t iValue2 = strtoull( "18446744073709551615", NULL, 10 );
printf( "%llu\n", iValue );
printf( "%llu\n", iValue2 );
return 0;
}
64bit 리눅스에서 위의 프로그램 실행 결과는 다음과 같다. 64bit 리눅스에서는 unsigned long 이 64bit 이므로 strtoul 과 strtoull 이 동일하게 동작한다.
18446744073709551615
18446744073709551615
32bit 리눅스에서 위의 프로그램 실행 결과는 다음과 같다. 32bit 리눅스에서는 unsigned long 이 32bit 이므로 strtoul 은 32bit 만 리턴하고 strtoull 이 64bit 를 리턴한다.
4294967295
18446744073709551615
