std::setw
From cppreference.com
| Defined in header <iomanip>
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| /*unspecified*/ setw( int n ); |
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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
- 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
| manages field width (public member function of std::ios_base) | |
| changes the fill character (function template) | |
| sets the placement of fill characters (function) |