NAME
ungetc —
un-get character from input
stream
LIBRARY
library “libc”
SYNOPSIS
#include
<stdio.h>
int
ungetc(int
c, FILE
*stream);
DESCRIPTION
Theungetc()
function pushes the character c (converted to an
unsigned char) back onto the input stream pointed to by
stream. The pushed-back 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 file-position indicator
is decremented by each successful call to
ungetc();
if its value was 0 before a call, its value is unspecified after the
call.
RETURN VALUES
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 remain unchanged.
SEE ALSO
STANDARDS
The ungetc() function conforms to
ISO/IEC 9899:1990
(“ISO C90”).