std::dec,std::hex,std::oct (3) Linux Manual Page

std::dec,std::hex,std::oct – std::dec,std::hex,std::oct

Synopsis

Defined in header <ios>
std::ios_base& dec( std::ios_base& str ); (1)
std::ios_base& hex( std::ios_base& str ); (2)
std::ios_base& oct( std::ios_base& str ); (3)
Modifies the default numeric base for integer I/O.
1) sets the basefield of the stream str to dec as if by calling str.setf(std::ios_base::dec, std::ios_base::basefield)
2) sets the basefield of the stream str to hex as if by calling str.setf(std::ios_base::hex, std::ios_base::basefield)
3) sets the basefield of the stream str to oct as if by calling str.setf(std::ios_base::oct, std::ios_base::basefield)
This is an I/O manipulator. It may be called with an expression such as out << std::hex for any out of type std::basic_ostream or with an expression such as in >> std::hex for any in of type std::basic_istream.

Parameters

str – reference to I/O stream

Return value

str (reference to the stream after manipulation)

Example

// Run this code

#include <iostream>

#include <sstream>

int main()

{
    std::cout << "The number 42 in octal:   " << std::oct << 42 << '\n'
              << "The number 42 in decimal: " << std::dec << 42 << '\n'
              << "The number 42 in hex:     " << std::hex << 42 << '\n';
    int n;
    std::istringstream("2A") >> std::hex >> n;
    std::cout << std::dec << "Parsing \"2A\" as hex gives " << n << '\n';
    // the output base is sticky until changed
    std::cout << std::hex << "42 as hex gives " << 42
              << " and 21 as hex gives " << 21 << '\n';
}

Output:

  The number 42 in octal: 52
  The number 42 in decimal: 42
  The number 42 in hex: 2a
  Parsing "2A" as hex gives 42
  42 as hex gives 2a and 21 as hex gives 15

See also

           changes the base used for integer I/O
setbase (function)
           controls whether prefix is used to indicate numeric base
showbase (function)
noshowbase