git.saurik.com Git - apple/libc.git/blame_incremental

... / ...

Commit	Line	Data
	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	.\" 4. Neither the name of the University nor the names of its contributors
	17	.\" may be used to endorse or promote products derived from this software
	18	.\" without specific prior written permission.
	19	.\"
	20	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	21	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	22	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	23	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	24	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	25	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	26	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	27	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	28	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	29	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	30	.\" SUCH DAMAGE.
	31	.\"
	32	.\" @(#)ungetc.3 8.1 (Berkeley) 6/4/93
	33	.\" $FreeBSD: src/lib/libc/stdio/ungetc.3,v 1.14 2007/01/09 00:28:07 imp Exp $
	34	.\"
	35	.Dd June 4, 1993
	36	.Dt UNGETC 3
	37	.Os
	38	.Sh NAME
	39	.Nm ungetc
	40	.Nd un-get character from input stream
	41	.Sh LIBRARY
	42	.Lb libc
	43	.Sh SYNOPSIS
	44	.In stdio.h
	45	.Ft int
	46	.Fo ungetc
	47	.Fa "int c"
	48	.Fa "FILE *stream"
	49	.Fc
	50	.Sh DESCRIPTION
	51	The
	52	.Fn ungetc
	53	function pushes the character
	54	.Fa c
	55	(converted to an unsigned char)
	56	back onto the input stream pointed to by
	57	.Fa stream .
	58	The pushed-back characters will be returned (in reverse order)
	59	by subsequent reads on the stream.
	60	A successful intervening call
	61	to one of the file positioning functions
	62	.Xr ( fseek 3 ,
	63	.Xr fsetpos 3 ,
	64	or
	65	.Xr rewind 3 ) ,
	66	using the same stream,
	67	will discard the pushed-back characters.
	68	.Pp
	69	Only one character of push-back is guaranteed,
	70	but as long as there is sufficient memory,
	71	an effectively infinite amount of push-back is allowed.
	72	.Pp
	73	If a character is successfully pushed-back,
	74	the end-of-file indicator for the stream is cleared.
	75	The file-position indicator is decremented
	76	by each successful call to
	77	.Fn ungetc ;
	78	if its value was 0 before a call, its value is unspecified after
	79	the call.
	80	.Sh RETURN VALUES
	81	The
	82	.Fn ungetc
	83	function returns the character pushed-back after the conversion,
	84	or
	85	.Dv EOF
	86	if the operation fails.
	87	If the value of the argument
	88	.Fa c
	89	character equals
	90	.Dv EOF ,
	91	the operation will fail and the stream will remain unchanged.
	92	.Sh SEE ALSO
	93	.Xr fseek 3 ,
	94	.Xr getc 3 ,
	95	.Xr setvbuf 3 ,
	96	.Xr ungetwc 3
	97	.Sh STANDARDS
	98	The
	99	.Fn ungetc
	100	function conforms to
	101	.St -isoC .