UNGETC(3) Library Functions Manual UNGETC(3)
ungetc -- un-get character from input stream
Standard C Library (libc, -lc)
ungetc(int c, FILE *stream);
The ungetc() function pushes the character c (converted to an unsigned
char) back onto the input stream pointed to by stream. The pushed-backed
characters will be returned by subsequent reads on the stream (in reverse
order). A successful intervening call, using the same stream, to one of
the file positioning functions (fseek(3), fsetpos(3), or rewind(3)) will
discard the pushed back characters.
One character of push-back is guaranteed, but as long as there is
sufficient memory, an effectively infinite amount of pushback is allowed.
If a character is successfully pushed-back, the end-of-file indicator for
the stream is cleared.
The ungetc() function returns the character pushed-back after the
conversion, or EOF if the operation fails. If the value of the argument
c character equals EOF, the operation will fail and the stream will
fseek(3), getc(3), setvbuf(3)
The ungetc() function conforms to ANSI X3.159-1989 (``ANSI C89'') and
IEEE Std 1003.1-2001 (``POSIX.1'').
An ungetc() function appeared in Version 7 AT&T UNIX.
NetBSD 6.1.5 April 30, 2010 NetBSD 6.1.5