Defined in header <cstdlib>  

unsigned long strtoul( const char* str, char** str_end, int base );  (1)  
unsigned long long strtoull( const char* str, char** str_end, int base );  (2)  (since C++11) 
Interprets an unsigned integer value in a byte string pointed to by str
.
Discards any whitespace characters (as identified by calling std::isspace
) until the first nonwhitespace character is found, then takes as many characters as possible to form a valid basen (where n=base
) unsigned integer number representation and converts them to an integer value. The valid unsigned integer value consists of the following parts:
0
) indicating octal base (applies only when the base is 8
or 0
) 0x
or 0X
) indicating hexadecimal base (applies only when the base is 16
or 0
) The set of valid values for base is {0,2,3,...,36}.
The set of valid digits for base2
integers is {0,1},
for base3
integers is {0,1,2},
and so on. For bases larger than 10
, valid digits include alphabetic characters, starting from Aa
for base11
integer, to Zz
for base36
integer. The case of the characters is ignored.
Additional numeric formats may be accepted by the currently installed C locale.
If the value of base
is 0
, the numeric base is autodetected: if the prefix is 0
, the base is octal, if the prefix is 0x
or 0X
, the base is hexadecimal, otherwise the base is decimal.
If the minus sign was part of the input sequence, the numeric value calculated from the sequence of digits is negated as if by unary minus in the result type, which applies unsigned integer wraparound rules.
The functions sets the pointer pointed to by str_end
to point to the character past the last character interpreted. If str_end
is a null pointer, it is ignored.
str    pointer to the nullterminated byte string to be interpreted 
str_end    pointer to a pointer to character, might be set to a position past the last character interpreted 
base    base of the interpreted integer value 
Integer value corresponding to the contents of str
on success. If the converted value falls out of range of corresponding return type, range error occurs (errno
is set to ERANGE
) and ULONG_MAX
or ULLONG_MAX
is returned. If no conversion can be performed, 0
is returned.
#include <cstdlib> #include <errno.h> #include <iostream> #include <string> int main() { const char* p = "10 200000000000000000000000000000 30 40  42"; char *end = nullptr; std::cout << "Parsing '" << p << "':\n"; for (unsigned long i = std::strtoul(p, &end, 10); p != end; i = std::strtoul(p, &end, 10)) { std::cout << "'" << std::string(p, end  p) << "' > "; p = end; if (errno == ERANGE) { errno = 0; std::cout << "range error, got "; } std::cout << i << '\n'; } std::cout << "After the loop p points to '" << p << "'\n"; }
Possible output:
Parsing '10 200000000000000000000000000000 30 40  42': '10' > 10 ' 200000000000000000000000000000' > range error, got 18446744073709551615 ' 30' > 30 ' 40' > 18446744073709551576 After the loop p points to '  42'
(C++11)(C++11)  converts a string to an unsigned integer (function) 
(C++11)  converts a byte string to an integer value (function) 
(C++11)(C++11)  converts a byte string to std::intmax_t or std::uintmax_t (function) 
converts a wide string to an unsigned integer value (function) 

converts a byte string to a floating point value (function) 

(C++17)  converts a character sequence to an integer or floatingpoint value (function) 
(C++11)  converts a byte string to an integer value (function) 
C documentation for strtoul, strtoull 
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