1.\" $NetBSD: fread.3,v 1.8 2001/01/25 02:06:25 lukem Exp $ 2.\" 3.\" Copyright (c) 1990, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" This code is derived from software contributed to Berkeley by 7.\" Chris Torek and the American National Standards Committee X3, 8.\" on Information Processing Systems. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 3. All advertising materials mentioning features or use of this software 19.\" must display the following acknowledgement: 20.\" This product includes software developed by the University of 21.\" California, Berkeley and its contributors. 22.\" 4. Neither the name of the University nor the names of its contributors 23.\" may be used to endorse or promote products derived from this software 24.\" without specific prior written permission. 25.\" 26.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36.\" SUCH DAMAGE. 37.\" 38.\" @(#)fread.3 8.2 (Berkeley) 3/8/94 39.\" 40.Dd March 8, 1994 41.Dt FREAD 3 42.Os 43.Sh NAME 44.Nm fread , 45.Nm fwrite 46.Nd binary stream input/output 47.Sh LIBRARY 48.Lb libc 49.Sh SYNOPSIS 50.Fd #include <stdio.h> 51.Ft size_t 52.Fn fread "void * restrict ptr" "size_t size" "size_t nmemb" "FILE * restrict stream" 53.Ft size_t 54.Fn fwrite "const void * restrict ptr" "size_t size" "size_t nmemb" "FILE * restrict stream" 55.Sh DESCRIPTION 56The function 57.Fn fread 58reads 59.Fa nmemb 60objects, each 61.Fa size 62bytes long, from the stream pointed to by 63.Fa stream , 64storing them at the location given by 65.Fa ptr . 66.Pp 67The function 68.Fn fwrite 69writes 70.Fa nmemb 71objects, each 72.Fa size 73bytes long, to the stream pointed to by 74.Fa stream , 75obtaining them from the location given by 76.Fa ptr . 77.Sh RETURN VALUES 78The functions 79.Fn fread 80and 81.Fn fwrite 82advance the file position indicator for the stream 83by the number of bytes read or written. 84They return the number of objects read or written. 85If 86.Fa size 87or 88.Fa nmemb 89is 0, the functions return 0 and the state of 90.Fa stream 91remains unchanged. 92If an error occurs, or the end-of-file is reached, 93the return value is a short object count (or zero). 94.Pp 95The function 96.Fn fread 97does not distinguish between end-of-file and error, and callers 98must use 99.Xr feof 3 100and 101.Xr ferror 3 102to determine which occurred. 103The function 104.Fn fwrite 105returns a value less than 106.Fa nmemb 107only if a write error has occurred. 108.Sh SEE ALSO 109.Xr read 2 , 110.Xr write 2 111.Sh STANDARDS 112The functions 113.Fn fread 114and 115.Fn fwrite 116conform to 117.St -ansiC . 118