std::setw

Defined in header <iomanip>
/unspecified/ setw( int n );

When used in an expression out << setw(n) or in >> setw(n), sets the width parameter of the stream out or in to exactly n.

Parameters

n	-	new value for width

Return value

Returns an object of unspecified type such that if str is the name of an output stream of type std::basic_ostream<CharT, Traits> or std::basic_istream<CharT, Traits>, then the expression str << setw(n) or str >> setw(n) behaves as if the following code was executed:

str.width(n);

Notes

The width property of the stream will be reset to zero (meaning "unspecified") if any of the following functions are called:

Input
- operator>>(basic_istream&, basic_string&)
- operator>>(basic_istream&, char*)
Output
- Overloads 1-7 of basic_ostream::operator<<() (at Stage 3 of num_put::put())
- operator<<(basic_ostream&, char) and operator<<(basic_ostream&, char*)
- operator<<(basic_ostream&, basic_string&)
- std::put_money (inside money_put::put())
- std::quoted (when used with an output stream)

The exact effects this modifier has on the input and output vary between the individual I/O functions and are described at each operator<< and operator>> overload page individually.

Example

#include <sstream>
#include <iostream>
#include <iomanip>
 
int main()
{
    std::cout << "no setw:" << 42 << '\n'
              << "setw(6):" << std::setw(6) << 42 << '\n'
              << "setw(6), several elements: " << 89 << std::setw(6) << 12 << 34 << '\n';
    std::istringstream is("hello, world");
    char arr[10];
    is >> std::setw(6) >> arr;
    std::cout << "Input from \"" << is.str() << "\" with setw(6) gave \""
              << arr << "\"\n";
}

Output:

no setw:42
setw(6):    42
setw(6), several elements: 89    1234
Input from "hello, world" with setw(6) gave "hello"

width	manages field width (public member function of std::ios_base)
setfill	changes the fill character (function template)
internalleftright	sets the placement of fill characters (function)

Parameters

Return value

Notes

Example

See also