Puts the characterch back to the input stream so the next extracted character will bech.

First clearseofbit, then behaves asUnformattedInputFunction. After constructing and checking the sentry object, ifrdbuf() is not null, callsrdbuf()->sputbackc(ch), which callsrdbuf()->pbackfail(ch) ifch does not equal the most recently extracted character.

Ifrdbuf() is null or ifrdbuf->sputbackc(ch) returnsTraits::eof(), callssetstate(badbit).

In any case, sets thegcount() counter to zero.

[edit]Parameters

[edit]Return value

*this

[edit]Exceptions

If an internal operation throws an exception, it is caught andbadbit is set. Ifexceptions() is set forbadbit, the exception is rethrown.

[edit]Example

#include <iostream>#include <sstream> int main(){std::stringstream s1("Hello, world");// IO stream    s1.get();if(s1.putback('Y'))// modifies the bufferstd::cout<< s1.rdbuf()<<'\n';elsestd::cout<<"putback failed\n"; std::cout<<"--\n"; std::istringstream s2("Hello, world");// input-only stream    s2.get();if(s2.putback('Y'))// cannot modify input-only bufferstd::cout<< s2.rdbuf()<<'\n';elsestd::cout<<"putback failed\n";     s2.clear(); std::cout<<"--\n"; if(s2.putback('H'))// non-modifying putbackstd::cout<< s2.rdbuf()<<'\n';elsestd::cout<<"putback failed\n";}

Yello, world--putback failed--Hello, world

[edit]Defect reports

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

[edit]See also

• In other languages

• Deutsch
• Español
• Français
• Italiano
• 日本語
• Português
• Русский
• 中文