ungetc(3s)
NAME
ungetc − push character back into input stream
SYNTAX
#include <stdio.h>
int ungetc(c, stream)
int c;
FILE *stream;
DESCRIPTION
The ungetc subroutine pushes the character c back on an input stream. That character will be returned by the next getc call on that stream. The ungetc subroutine returns c.
One character of pushback is guaranteed provided something has been read from the stream and the stream is actually buffered. Attempts to push EOF are rejected.
If c equals EOF, ungetc does nothing to the buffer and returns EOF.
The fseek subroutine erases all memory of pushed back characters.
DIAGNOSTICS
The ungetc subroutine returns EOF if it can’t push a character back.