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.\" @(#)fread.3 8.2 (Berkeley) 3/8/94 33.\" $FreeBSD$ 34.\" 35.Dd March 8, 1994 36.Dt FREAD 3 37.Os 38.Sh NAME 39.Nm fread , 40.Nm fwrite 41.Nd binary stream input/output 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.In stdio.h 46.Ft size_t 47.Fn fread "void * restrict ptr" "size_t size" "size_t nmemb" "FILE * restrict stream" 48.Ft size_t 49.Fn fwrite "const void * restrict ptr" "size_t size" "size_t nmemb" "FILE * restrict stream" 50.Sh DESCRIPTION 51The function 52.Fn fread 53reads 54.Fa nmemb 55objects, each 56.Fa size 57bytes long, from the stream pointed to by 58.Fa stream , 59storing them at the location given by 60.Fa ptr . 61.Pp 62The function 63.Fn fwrite 64writes 65.Fa nmemb 66objects, each 67.Fa size 68bytes long, to the stream pointed to by 69.Fa stream , 70obtaining them from the location given by 71.Fa ptr . 72.Sh RETURN VALUES 73The functions 74.Fn fread 75and 76.Fn fwrite 77advance the file position indicator for the stream 78by the number of bytes read or written. 79They return the number of objects read or written. 80If an error occurs, or the end-of-file is reached, 81the return value is a short object count (or zero). 82.Pp 83The function 84.Fn fread 85does not distinguish between end-of-file and error, and callers 86must use 87.Xr feof 3 88and 89.Xr ferror 3 90to determine which occurred. 91The function 92.Fn fwrite 93returns a value less than 94.Fa nmemb 95only if a write error has occurred. 96.Sh SEE ALSO 97.Xr read 2 , 98.Xr write 2 99.Sh STANDARDS 100The functions 101.Fn fread 102and 103.Fn fwrite 104conform to 105.St -isoC . 106