std::ws

Header: <istream>

Discards leading whitespace from an input stream.

# Declarations

template< class CharT, class Traits >
std::basic_istream<CharT, Traits>& ws( std::basic_istream<CharT, Traits>& is );

# Parameters

is: reference to input stream

# Return value

is (reference to the stream after extraction of consecutive whitespace).

# Notes

If eofbit is set on the stream prior to the call, the construction of the sentry object will set failbit.

# Example

#include <iomanip>
#include <iostream>
#include <istream>
#include <sstream>
#include <string>
 
int main()
{
    for (const char* str : {"     #1 test", "\t #2 test", "#3 test"})
    {
        std::string line;
        std::getline(std::istringstream{str}, line);
        std::cout << "getline returns:\t" << std::quoted(line) << '\n';
 
        std::istringstream iss{str};
        std::getline(iss >> std::ws, line);
        std::cout << "ws + getline returns:\t" << std::quoted(line) << '\n';
    }
}

# Defect reports

DR	Applied to	Behavior as published	Correct behavior
LWG 415	C++98	calling std::ws might not construct the sentryobject (insonsistent with other input functions)	required to constructthe sentry object

# See also

ignore