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std::left, std::right, std::internal - cppreference.com

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Defined in header <ios>

std::ios_base& left( std::ios_base& str );

 (1)

std::ios_base& right( std::ios_base& str );

 (2)

std::ios_base& internal( std::ios_base& str );

 (3)

Modifies the positioning of the fill characters in an output stream. left and right apply to any type being output, internal applies to integer, floating-point, and monetary output. Has no effect on input.

1) Sets the adjustfield of the stream str to left as if by calling str.setf(std::ios_base::left, std::ios_base::adjustfield).

2) Sets the adjustfield of the stream str to right as if by calling str.setf(std::ios_base::right, std::ios_base::adjustfield).

3) Sets the adjustfield of the stream str to internal as if by calling str.setf(std::ios_base::internal, std::ios_base::adjustfield).

The initial default for standard streams is equivalent to right.

This is an I/O manipulator. It may be called with an expression such as out << std::left for any out of type std::basic_ostream or with an expression such as in >> std::left 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

#include <iomanip>
#include <iostream>
#include <locale>

int main()
{
    std::cout.imbue(std::locale("en_US.utf8"));

    std::cout << "Default positioning:\n" << std::setfill('*')
              << std::setw(12) << -1.23  << '\n'
              << std::setw(12) << std::hex << std::showbase << 42 << '\n'
              << std::setw(12) << std::put_money(123, true) << "\n\n";
              
    std::cout << "Left positioning:\n" << std::left
              << std::setw(12) << -1.23  << '\n'
              << std::setw(12) << 42 << '\n'
              << std::setw(12) << std::put_money(123, true) << "\n\n";

    std::cout << "Internal positioning:\n" << std::internal
              << std::setw(12) << -1.23  << '\n'
              << std::setw(12) << 42 << '\n'
              << std::setw(12) << std::put_money(123, true) << "\n\n";

    std::cout << "Right positioning:\n" << std::right
              << std::setw(12) << -1.23  << '\n'
              << std::setw(12) << 42 << '\n'
              << std::setw(12) << std::put_money(123, true) << '\n';
}

Output: 

Default positioning:
*******-1.23
********0x2a
***USD *1.23

Left positioning:
-1.23*******
0x2a********
USD *1.23***

Internal positioning:
-*******1.23
0x********2a
USD ****1.23

Right positioning:
*******-1.23
********0x2a
***USD *1.23

See also