std::strtol, std::strtoll

< cpp‎ | string‎ | byte
Defined in header <cstdlib>
long      strtol( const char *str, char **str_end, int base );
long long strtoll( const char *str, char **str_end, int base );
(since C++11)

Interprets an integer value in a byte string pointed to by str.

Function discards any whitespace characters (as identified by calling isspace()) until first non-whitespace character is found. Then it takes as many characters as possible to form a valid base-n (where n=base) integer number representation and converts them to an integer value. The valid integer value consists of the following parts:

  • (optional) plus or minus sign
  • (optional) prefix (0) indicating octal base (applies only when the base is 8 or 0)
  • (optional) prefix (0x or 0X) indicating hexadecimal base (applies only when the base is 16 or 0)
  • a sequence of digits

The set of valid digits for base-2 integer is 01, for base-3 integer is 012, and so on. For bases larger than 10, valid digits include alphabetic characters, starting from Aa for base-11 integer, to Zz for base-36 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 auto-detected: 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.

The functions sets the pointer pointed to by str_end to point to the character past the last character interpreted. If str_end is NULL, it is ignored.

If the str is empty or does not have the expected form, no conversion is performed, and (if str_end is not NULL) the value of str is stored in the object pointed to by str_end.


[edit] Parameters

str - pointer to the null-terminated byte string to be interpreted
str_end - pointer to a pointer to character.
base - base of the interpreted integer value

[edit] Return value

  • If successful, an integer value corresponding to the contents of str is returned.
  • If the converted value falls out of range of corresponding return type, a range error occurs (setting errno to ERANGE) and LONG_MAX, LONG_MIN, LLONG_MAX or LLONG_MIN is returned.
  • If no conversion can be performed, 0 is returned.

[edit] Example

#include <iostream>
#include <cstdlib>
int main()
    const char* begin = "10 20000000000000000000000 30 40";
    char *end;
    for (long i = std::strtol(begin, &end, 10);
         begin != end;
         i = std::strtol(begin, &end, 10))
        begin = end;
        if (errno == ERANGE){
            std::cout << "range error\n";
            errno = 0;
        std::cout << i << '\n';


range error

[edit] See also

converts a byte string to an integer value
converts a byte string to an unsigned integer value
C documentation for strtol, strtoll