NAME¶

std::setw - std::setw

Synopsis¶

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¶

// Run this code

#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"

See also¶

width manages field width
(public member function of std::ios_base)
setfill changes the fill character
(function template)
internal sets the placement of fill characters
left (function)
right
showbase controls whether prefix is used to indicate numeric base
noshowbase (function)