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 SYNOPSIS 46.Fd #include <stdio.h> 47.Ft int 48.Fn ungetc "int c" "FILE *stream" 49.Sh DESCRIPTION 50The 51.Fn ungetc 52function pushes the character 53.Fa c 54(converted to an unsigned char) 55back onto the input stream pointed to by 56.Fa stream . 57The pushed-backed characters will be returned by subsequent reads on the 58stream (in reverse order). 59A successful intervening call, using the same stream, to one of the file 60positioning functions 61.Po 62.Xr fseek 3 , 63.Xr fsetpos 3 , 64or 65.Xr rewind 3 66.Pc 67will discard the pushed back characters. 68.Pp 69One character of push-back is guaranteed, 70but as long as there is 71sufficient memory, an effectively infinite amount of pushback is allowed. 72.Pp 73If a character is successfully pushed-back, 74the end-of-file indicator for the stream is cleared. 75.Sh RETURN VALUES 76The 77.Fn ungetc 78function 79returns 80the character pushed-back after the conversion, or 81.Dv EOF 82if the operation fails. 83If the value of the argument 84.Fa c 85character equals 86.Dv EOF , 87the operation will fail and the stream will remain unchanged. 88.Sh SEE ALSO 89.Xr fseek 3 , 90.Xr getc 3 , 91.Xr setvbuf 3 92.Sh STANDARDS 93The 94.Fn ungetc 95function conforms to 96.St -ansiC . 97