std::setw

From cppreference.com
< cpp | io | manip
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. This value is not "sticky": the next input or output operation that is affected by the value of the stream's width field, resets it to zero (meaning "unspecified").

Contents

[edit] Parameters

n - new value for width

[edit] 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);

[edit] Example

#include <sstream>
#include <iostream>
#include <iomanip>
int main()
{
        std::cout << "no setw: " << 42 << '\n'
                  << "setw(6): " << std::setw(6) << 42 << '\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
Input from "hello, world" with setw(6) gave "hello"

[edit] See also

manages field width
(public member function of std::ios_base)
changes the fill character
(function template)