# strtol
NAME
strtol, strtoll, strtoq - convert a string to a long integer
SYNOPSIS
#include <stdlib.h>
long int strtol(const char *nptr, char **endptr, int base);
long long int strtoll(const char *nptr, char **endptr, int base);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
strtoll(): XOPEN_SOURCE >= 600 || _BSD_SOURCE || _SVID_SOURCE || _ISOC99_SOURCE; or cc -std=c99
DESCRIPTION
The strtol() function converts the initial part of the string in nptr to a long integer 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 a long int value in the obvious manner, stopping at the first char-
acter 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, strtol() stores the address of the first invalid character in *endptr. If there were no
digits at all, strtol() 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 strtoll() function works just like the strtol() function but returns a long long integer value.
RETURN VALUE
The strtol() function returns the result of the conversion, unless the value would underflow or overflow. If
an underflow occurs, strtol() returns LONG_MIN. If an overflow occurs, strtol() returns LONG_MAX. In both
cases, errno is set to ERANGE. Precisely the same holds for strtoll() (with LLONG_MIN and LLONG_MAX instead of
LONG_MIN and LONG_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
strtol() conforms to SVr4, 4.3BSD, C89, C99 and POSIX.1-2001, and strtoll() to C99 and POSIX.1-2001.
NOTES
Since strtol() can legitimately return 0, LONG_MAX, or LONG_MIN (LLONG_MAX or LLONG_MIN for strtoll()) 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 also be accepted. (For example, the thousands separa-
tor of the current locale may be supported.)
BSD also has
quad_t strtoq(const char *nptr, char **endptr, int base);
with completely analogous definition. Depending on the wordsize of the current architecture, this may be
equivalent to strtoll() or to strtol().
EXAMPLE
The program shown below demonstrates the use of strtol(). The first command-line argument specifies a string
from which strtol() should parse a number. The second (optional) argument specifies the base to be used for
the conversion. (This argument is converted to numeric form using atoi(3), a function that performs no error
checking and has a simpler interface than strtol().) Some examples of the results produced by this program are
the following:
$ ./a.out 123
strtol() returned 123
$ ./a.out ' 123'
strtol() returned 123
$ ./a.out 123abc
strtol() returned 123
Further characters after number: abc
$ ./a.out 123abc 55
strtol: Invalid argument
$ ./a.out ''
No digits were found
$ ./a.out 4000000000
strtol: Numerical result out of range
Program source
#include <stdlib.h>
#include <limits.h>
#include <stdio.h>
#include <errno.h>
int
main(int argc, char *argv[])
{
int base;
char *endptr, *str;
long val;
if (argc < 2) {
fprintf(stderr, "Usage: %s str [base]\n", argv[0]);
exit(EXIT_FAILURE);
}
str = argv[1];
base = (argc > 2) ? atoi(argv[2]) : 10;
errno = 0; /* To distinguish success/failure after call */
val = strtol(str, &endptr, base);
/* Check for various possible errors */
if ((errno == ERANGE && (val == LONG_MAX || val == LONG_MIN))
|| (errno != 0 && val == 0)) {
perror("strtol");
exit(EXIT_FAILURE);
}
if (endptr == str) {
fprintf(stderr, "No digits were found\n");
exit(EXIT_FAILURE);
}
/* If we got here, strtol() successfully parsed a number */
printf("strtol() returned %ld\n", val);
if (*endptr != '\0') /* Not necessarily an error... */
printf("Further characters after number: %s\n", endptr);
exit(EXIT_SUCCESS);
}
SEE ALSO
atof(3), atoi(3), atol(3), strtod(3), strtoul(3)
-----------------------------------------------------------------------------------------------------------
//C언어 표준 라이브러리 함수 사용법 가이드
//long long strtoll(const char * nptr,char **endptr,int base); 정수로 구성한 문자열로 long long 형식 값을 구함
//문자열의 정수를 원하는 진수 체계의 정수로 계산하여 출력
#include <stdlib.h>
#include <stdio.h>
int main(void)
{
char src[100] = "1234567890 123456789abcdef 16 100111111111111110000001100111110011110";
char *pos = NULL;
long long value1 = 0, value2 = 0, value3 = 0, value4 = 0;
value1 = strtoll(src, &pos, 10);//10진수로 계산
value2 = strtoll(pos, &pos, 16);//16진수로 계산
value3 = strtoll(pos, &pos, 8);//8진수로 계산
value4 = strtoll(pos, &pos, 2); //2진수로 계산
printf("%lld %lld %lld %lld\n", value1, value2, value3, value4);
return 0;
}
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