std::strtoimax,std::strtoumax(3)

NAME
std::strtoimax,std::strtoumax - std::strtoimax,std::strtoumax

Synopsis
   Defined in header <cinttypes>
   std::intmax_t strtoimax( const char* nptr, char** endptr, int base ); (since C++11)
   std::uintmax_t strtoumax( const char* nptr, char** endptr, int base (since C++11)
   );
   Interprets an integer value in a byte string pointed to by nptr.
   Discards any whitespace characters (as identified by calling std::isspace) until the
   first non-whitespace character is found, then 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 values for base is {0,2,3,...,36}. The set of valid digits for
   base-2 integers is {0,1}, for base-3 integers is {0,1,2}, 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.
   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.
   The functions sets the pointer pointed to by endptr to point to the character past
   the last character interpreted. If endptr is a null pointer, it is ignored.
   If the nptr is empty or does not have the expected form, no conversion is performed,
   and (if enptr is not a null pointer) the value of nptr is stored in the object
   pointed to by endptr.

Parameters
   nptr - pointer to the null-terminated byte string to be interpreted
   endptr - pointer to a pointer to character.
   base - base of the interpreted integer value

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 INTMAX_MAX, INTMAX_MIN, UINTMAX_MAX
       or 0 is returned, as appropriate.
     * If no conversion can be performed, 0 is returned.

Example
// Run this code
 #include <iostream>
 #include <string>
 #include <cinttypes>
 int main()
 {
     std::string str = "helloworld";
     std::intmax_t val = std::strtoimax(str.c_str(), nullptr, 36);
     std::cout << str << " in base 36 is " << val << " in base 10\n";
     char* nptr;
     val = std::strtoimax(str.c_str(), &nptr, 30);
     if(nptr != &str[0] + str.size())
         std::cout << str << " in base 30 is invalid."
                   << " The first invalid digit is '" << *nptr << "'\n";
 }

Output:
 helloworld in base 36 is 1767707668033969 in base 10
 helloworld in base 30 is invalid. The first invalid digit is 'w'

See also
   stoi
   stol
   stoll converts a string to a signed integer
   (C++11) (function)
   (C++11)
   (C++11)
   stoul
   stoull converts a string to an unsigned integer
   (C++11) (function)
   (C++11)
   strtol converts a byte string to an integer value
   strtoll (function)
   (C++11)
   strtoul converts a byte string to an unsigned integer value
   strtoull (function)
   (C++11)
   wcstoimax
   wcstoumax converts a wide string to std::intmax_t or std::uintmax_t
   (C++11) (function)
   (C++11)
   strtof converts a byte string to a floating point value
   strtod (function)
   strtold
   from_chars converts a character sequence to an integer or floating-point value
   (C++17) (function)
   atoi
   atol converts a byte string to an integer value
   atoll (function)
   (C++11)