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std::ws

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< cpp‎ | io‎ | manip
Revision as of 13:15, 21 November 2013 by Cubbi (Talk | contribs)

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

Discards leading whitespace from an input stream.

Behaves as an UnformattedInputFunction, except that is.gcount() is not modified. After constructing and checking the sentry object, extracts characters from the stream and discards them until any one of the following conditions occurs:

  • end of file condition occurs in the input sequence (in which case the function calls setstate(eofbit) but does not set failbit.
  • the next available character c in the input sequence is not whitespace as determined by std::isspace(c, is.getloc()). The non-whitespace character is not extracted.

This is an input-only I/O manipulator, it may be called with an expression such as in >> std::ws for any in of type std::basic_istream.

Contents

[edit] Parameters

is - reference to input stream

[edit] Return value

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

[edit] Example

#include <iostream>
#include <sstream>
 
int main()
{
    std::istringstream s("     this is a test");
    std::string line;
    getline(s >> std::ws, line);
    std::cout << "ws + getline returns: \"" << line << "\"\n";
}

Output:

ws + getline returns: "this is a test"

[edit] See also

extracts and discards characters until the given character is found
(public member function of std::basic_istream) [edit]