std::basic_istream<CharT,Traits>:: ignore

Extracts and discards characters from the input stream until and including delim .

ignore behaves as an UnformattedInputFunction . After constructing and checking the sentry object, it extracts characters from the stream and discards them until any of the following conditions occurs:

• count characters were extracted. This test is disabled in the special case when count equals std:: numeric_limits < std:: streamsize > :: max ( ) .

• end of file conditions occurs in the input sequence, in which case the function calls setstate ( eofbit ) .

• the next available character c in the input sequence is delim , as determined by Traits :: eq_int_type ( Traits :: to_int_type ( c ) , delim ) . The delimiter character is extracted and discarded. This test is disabled if delim is Traits :: eof ( ) .

Parameters

Return value

* this

Exceptions

If an internal operation throws an exception, it is caught and badbit is set. If exceptions() is set for badbit , the exception is rethrown.

Example

#include <iostream>
#include <limits>
#include <sstream>
 
constexpr auto max_size = std::numeric_limits<std::streamsize>::max();
 
int main()
{
    std::istringstream input("1\n"
                             "some non-numeric input\n"
                             "2\n");
    for (;;)
    {
        int n;
        input >> n;
 
        if (input.eof() || input.bad())
            break;
        else if (input.fail())
        {
            input.clear(); // unset failbit
            input.ignore(max_size, '\n'); // skip bad input
        }
        else
            std::cout << n << '\n';
    }
}

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Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

See also