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. 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.\" @(#)ferror.3 8.2 (Berkeley) 4/19/94 33.\" $FreeBSD: src/lib/libc/stdio/ferror.3,v 1.13 2009/01/28 14:38:41 trhodes Exp $ 34.\" $DragonFly: src/lib/libc/stdio/ferror.3,v 1.2 2003/06/17 04:26:45 dillon Exp $ 35.\" 36.Dd January 28, 2009 37.Dt FERROR 3 38.Os 39.Sh NAME 40.Nm clearerr , 41.Nm clearerr_unlocked , 42.Nm feof , 43.Nm feof_unlocked , 44.Nm ferror , 45.Nm ferror_unlocked , 46.Nm fileno , 47.Nm fileno_unlocked 48.Nd check and reset stream status 49.Sh LIBRARY 50.Lb libc 51.Sh SYNOPSIS 52.In stdio.h 53.Ft void 54.Fn clearerr "FILE *stream" 55.Ft void 56.Fn clearerr_unlocked "FILE *stream" 57.Ft int 58.Fn feof "FILE *stream" 59.Ft int 60.Fn feof_unlocked "FILE *stream" 61.Ft int 62.Fn ferror "FILE *stream" 63.Ft int 64.Fn ferror_unlocked "FILE *stream" 65.Ft int 66.Fn fileno "FILE *stream" 67.Ft int 68.Fn fileno_unlocked "FILE *stream" 69.Sh DESCRIPTION 70The function 71.Fn clearerr 72clears the end-of-file and error indicators for the stream pointed 73to by 74.Fa stream . 75.Pp 76The function 77.Fn feof 78tests the end-of-file indicator for the stream pointed to by 79.Fa stream , 80returning non-zero if it is set. 81The end-of-file indicator may be cleared by explicitly calling 82.Fn clearerr , 83or as a side-effect of other operations, e.g.\& 84.Fn fseek . 85.Pp 86The function 87.Fn ferror 88tests the error indicator for the stream pointed to by 89.Fa stream , 90returning non-zero if it is set. 91.Pp 92The function 93.Fn fileno 94examines the argument 95.Fa stream 96and returns its integer descriptor. 97.Pp 98The 99.Fn clearerr_unlocked , 100.Fn feof_unlocked , 101.Fn ferror_unlocked , 102and 103.Fn fileno_unlocked 104functions are equivalent to 105.Fn clearerr , 106.Fn feof , 107.Fn ferror , 108and 109.Fn fileno 110respectively, except that the caller is responsible for locking the stream 111with 112.Xr flockfile 3 113before calling them. 114These functions may be used to avoid the overhead of locking the stream 115and to prevent races when multiple threads are operating on the same stream. 116.Sh ERRORS 117These functions should not fail and do not set the external 118variable 119.Va errno . 120.Sh SEE ALSO 121.Xr open 2 , 122.Xr fdopen 3 , 123.Xr flockfile 3 , 124.Xr stdio 3 125.Sh STANDARDS 126The functions 127.Fn clearerr , 128.Fn feof , 129and 130.Fn ferror 131conform to 132.St -isoC . 133