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