std::basic_istream::unget

 

C++

Language

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Technical Specifications

 

Input/output library

I/O manipulators

C-style I/O

Buffers

basic_streambuf

basic_filebuf

basic_stringbuf

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ios_base

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basic_istream

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basic_stringstream

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istrstream (deprecated)

ostrstream (deprecated)

strstream (deprecated)

Types

streamoff

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iostream_category (C++11)

io_errc (C++11)

 

std::basic_istream

Global objects

cinwcin

Member functions

basic_istream::basic_istream

basic_istream::~basic_istream

basic_istream::operator= (C++11)

Formatted input

basic_istream::operator>>

Unformatted input

basic_istream::get

basic_istream::peek

basic_istream::unget

basic_istream::putback

basic_istream::getline

basic_istream::ignore

basic_istream::read

basic_istream::readsome

basic_istream::gcount

Positioning

basic_istream::tellg

basic_istream::seekg

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basic_istream::sync

basic_istream::swap (C++11)

Member classes

basic_istream::sentry

Non-member functions

operator>>(std::basic_istream)

 

basic_istream& unget();

Makes the most recently extracted character available again.

First clears eofbit.

(since C++11)

Then the function behaves as UnformattedInputFunction. After constructing and checking the sentry object, if any ios_base::iostate flags are set, the function sets failbit and returns. Otherwise, calls rdbuf()->sungetc().

If rdbuf()->sungetc() returns Traits::eof(), calls setstate(badbit).

In any case, sets the gcount() counter to zero.

Parameters

(none)

Return value

*this

Exceptions

failure if an error occurred (the error state flag is not goodbit) and exceptions() is set to throw for that state.

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

Run this code

#include <sstream>
#include <iostream>
 
int main()
{
    std::istringstream s1("Hello, world.");
    char c1 = s1.get();
    if (s1.unget())
    {
        char c2 = s1.get();
        std::cout << "Got: " << c1 << " got again: " << c2 << '\n';
    }
}

Output:

Got: H got again: H

See also

sungetc	moves the next pointer in the input sequence back by one (public member function of std::basic_streambuf)
get	extracts characters (public member function)
peek	reads the next character without extracting it (public member function)
putback	puts character into input stream (public member function)