If a putback position is available in the get area (gptr()> eback()), then decrements the next pointer (gptr()) and returns the character it now points to.

If a putback position is not available, then callspbackfail() to back up the input sequence if possible.

The I/O stream functionbasic_istream::unget is implemented in terms of this function.

[edit]Parameters

(none)

[edit]Return value

If putback position was available, returns the character that the next pointer is now pointing at, converted toint_type withTraits::to_int_type(*gptr()). The next single-character input from this streambuf will return this character.

If putback position was not available, returns whatpbackfail() returns, which isTraits::eof() on failure.

[edit]Example

#include <iostream>#include <sstream> int main(){std::stringstream s("abcdef");// gptr() points to 'a'char c1= s.get();// c = 'a', gptr() now points to 'b'char c2= s.rdbuf()->sungetc();// same as s.unget(): gptr() points to 'a' againchar c3= s.get();// c3 = 'a', gptr() now points to 'b'char c4= s.get();// c4 = 'b', gptr() now points to 'c'std::cout<< c1<< c2<< c3<< c4<<'\n';     s.rdbuf()->sungetc();// back to 'b'    s.rdbuf()->sungetc();// back to 'a'int eof= s.rdbuf()->sungetc();// nothing to unget: pbackfail() failsif(eof==EOF)std::cout<<"Nothing to unget after 'a'\n";}

aaabNothing to unget after 'a'

[edit]See also

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