1.\" Copyright (c) 1990, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" Chris Torek and the American National Standards Committee X3, 6.\" on Information Processing Systems. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. All advertising materials mentioning features or use of this software 17.\" must display the following acknowledgement: 18.\" This product includes software developed by the University of 19.\" California, Berkeley and its contributors. 20.\" 4. Neither the name of the University nor the names of its contributors 21.\" may be used to endorse or promote products derived from this software 22.\" without specific prior written permission. 23.\" 24.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34.\" SUCH DAMAGE. 35.\" 36.\" @(#)ungetc.3 8.1 (Berkeley) 6/4/93 37.\" $FreeBSD$ 38.\" 39.Dd June 4, 1993 40.Dt UNGETC 3 41.Os 42.Sh NAME 43.Nm ungetc 44.Nd un-get character from input stream 45.Sh LIBRARY 46.Lb libc 47.Sh SYNOPSIS 48.Fd #include <stdio.h> 49.Ft int 50.Fn ungetc "int c" "FILE *stream" 51.Sh DESCRIPTION 52The 53.Fn ungetc 54function pushes the character 55.Fa c 56(converted to an unsigned char) 57back onto the input stream pointed to by 58.Fa stream . 59The pushed-back characters will be returned by subsequent reads on the 60stream (in reverse order). 61A successful intervening call, 62using the same stream, 63to one of the file positioning functions 64.Po 65.Xr fseek 3 , 66.Xr fsetpos 3 , 67or 68.Xr rewind 3 69.Pc 70will discard the pushed back characters. 71.Pp 72One character of push-back is guaranteed, 73but as long as there is sufficient memory, 74an effectively infinite amount of pushback is allowed. 75.Pp 76If a character is successfully pushed-back, 77the end-of-file indicator for the stream is cleared. 78.Sh RETURN VALUES 79The 80.Fn ungetc 81function returns the character pushed-back after the conversion, 82or 83.Dv EOF 84if the operation fails. 85If the value of the argument 86.Fa c 87character equals 88.Dv EOF , 89the operation will fail and the stream will remain unchanged. 90.Sh SEE ALSO 91.Xr fseek 3 , 92.Xr getc 3 , 93.Xr setvbuf 3 94.Sh STANDARDS 95The 96.Fn ungetc 97function conforms to 98.St -isoC . 99