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.\" 34.Dd April 2, 2022 35.Dt FERROR 3 36.Os 37.Sh NAME 38.Nm clearerr , 39.Nm clearerr_unlocked , 40.Nm feof , 41.Nm feof_unlocked , 42.Nm ferror , 43.Nm ferror_unlocked , 44.Nm fileno , 45.Nm fileno_unlocked 46.Nd check and reset stream status 47.Sh LIBRARY 48.Lb libc 49.Sh SYNOPSIS 50.In stdio.h 51.Ft void 52.Fn clearerr "FILE *stream" 53.Ft void 54.Fn clearerr_unlocked "FILE *stream" 55.Ft int 56.Fn feof "FILE *stream" 57.Ft int 58.Fn feof_unlocked "FILE *stream" 59.Ft int 60.Fn ferror "FILE *stream" 61.Ft int 62.Fn ferror_unlocked "FILE *stream" 63.Ft int 64.Fn fileno "FILE *stream" 65.Ft int 66.Fn fileno_unlocked "FILE *stream" 67.Sh DESCRIPTION 68The function 69.Fn clearerr 70clears the end-of-file and error indicators for the stream pointed 71to by 72.Fa stream . 73.Pp 74The function 75.Fn feof 76tests the end-of-file indicator for the stream pointed to by 77.Fa stream , 78returning non-zero if it is set. 79The end-of-file indicator may be cleared by explicitly calling 80.Fn clearerr , 81or as a side-effect of other operations, e.g.\& 82.Fn fseek . 83.Pp 84The function 85.Fn ferror 86tests the error indicator for the stream pointed to by 87.Fa stream , 88returning non-zero if it is set. 89.Pp 90The function 91.Fn fileno 92examines the argument 93.Fa stream 94and returns its integer descriptor. 95.Pp 96The 97.Fn clearerr_unlocked , 98.Fn feof_unlocked , 99.Fn ferror_unlocked , 100and 101.Fn fileno_unlocked 102functions are equivalent to 103.Fn clearerr , 104.Fn feof , 105.Fn ferror , 106and 107.Fn fileno 108respectively, except that the caller is responsible for locking the stream 109with 110.Xr flockfile 3 111before calling them. 112These functions may be used to avoid the overhead of locking the stream 113and to prevent races when multiple threads are operating on the same stream. 114.Sh ERRORS 115These functions should not fail and do not set the external 116variable 117.Va errno . 118.Sh SEE ALSO 119.Xr open 2 , 120.Xr fdopen 3 , 121.Xr flockfile 3 , 122.Xr stdio 3 123.Sh STANDARDS 124The functions 125.Fn clearerr , 126.Fn feof , 127and 128.Fn ferror 129conform to 130.St -isoC . 131.Sh HISTORY 132The functions 133.Fn clearerr , 134.Fn feof , 135.Fn ferror , 136and 137.Fn fileno 138first appeared in 139.At v7 . 140