.\"	$OpenBSD: ungetc.3,v 1.6 2003/06/02 20:18:37 millert Exp $
.\"
.\" Copyright (c) 1990, 1991, 1993
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.\" This code is derived from software contributed to Berkeley by
.\" Chris Torek and the American National Standards Committee X3,
.\" on Information Processing Systems.
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.Dd June 4, 1993
.Dt UNGETC 3
.Os
.Sh NAME
.Nm ungetc
.Nd un-get character from input stream
.Sh SYNOPSIS
.Fd #include <stdio.h>
.Ft int
.Fn ungetc "int c" "FILE *stream"
.Sh DESCRIPTION
The
.Fn ungetc
function pushes the character
.Fa c
(converted to an
.Li unsigned char )
back onto the input stream pointed to by
.Fa 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
.Po
.Xr fseek 3 ,
.Xr fsetpos 3 ,
or
.Xr rewind 3
.Pc
will discard the pushed back characters.
.Pp
One character of push-back is guaranteed,
but as long as there is
sufficient memory, an effectively infinite amount of pushback is allowed.
.Pp
If a character is successfully pushed-back,
the end-of-file indicator for the stream is cleared.
.Sh RETURN VALUES
The
.Fn ungetc
function returns the character pushed-back after the conversion, or
.Dv EOF
if the operation fails.
If the value of the argument
.Fa c
character equals
.Dv EOF ,
the operation will fail and the stream will remain unchanged.
.Sh SEE ALSO
.Xr fseek 3 ,
.Xr getc 3 ,
.Xr setvbuf 3
.Sh STANDARDS
The
.Fn ungetc
function conforms to
.St -ansiC .