UNGETC(3S)
NAME
ungetc − push character back into input stream
USAGE
#include <stdio.h>
ungetc(c, stream) FILE *stream;
DESCRIPTION
Ungetc pushes the character c back into the named input stream. That character will be returned by the next getc call on that stream. Ungetc returns c.
One character of pushback is guaranteed, provided that something has been read from the stream and the stream is actually buffered. Attempts to putc an EOF are rejected.
Fseek(3S) erases all memory of pushed-back characters.
DIAGNOSTICS
Ungetc returns EOF if it can’t push a character back onto the named stream.