stdio/FreeBSD/ferror.3

   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 .\"     @(#)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 .\"
  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
  69 The function
  70 .Fn clearerr
  71 clears the end-of-file and error indicators for the stream pointed
  72 to by
  73 .Fa stream .
  74 .Pp
  75 The function
  76 .Fn feof
  77 tests the end-of-file indicator for the stream pointed to by
  78 .Fa stream ,
  79 returning non-zero if it is set.
  80 The end-of-file indicator may be cleared by explicitly calling
  81 .Fn clearerr ,
  82 or as a side-effect of other operations, e.g.\&
  83 .Fn fseek .
  84 .Pp
  85 The function
  86 .Fn ferror
  87 tests the error indicator for the stream pointed to by
  88 .Fa stream ,
  89 returning non-zero if it is set.
  90 .Pp
  91 The function
  92 .Fn fileno
  93 examines the argument
  94 .Fa stream
  95 and returns its integer descriptor.
  96 .Pp
  97 The
  98 .Fn clearerr_unlocked ,
  99 .Fn feof_unlocked ,
 100 .Fn ferror_unlocked ,
 101 and
 102 .Fn fileno_unlocked
 103 functions are equivalent to
 104 .Fn clearerr ,
 105 .Fn feof ,
 106 .Fn ferror ,
 107 and
 108 .Fn fileno
 109 respectively, except that the caller is responsible for locking the stream
 110 with
 111 .Xr flockfile 3
 112 before calling them.
 113 These functions may be used to avoid the overhead of locking the stream
 114 and to prevent races when multiple threads are operating on the same stream.
 115 .Sh ERRORS
 116 These functions should not fail and do not set the external
 117 variable
 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
 125 The functions
 126 .Fn clearerr ,
 127 .Fn feof ,
 128 and
 129 .Fn ferror
 130 conform to
 131 .St -isoC .