1.\" $OpenBSD: fread.3,v 1.2 1996/08/19 08:32:44 tholo 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.Dd March 8, 1994 39.Dt FREAD 3 40.Os 41.Sh NAME 42.Nm fread , 43.Nm fwrite 44.Nd binary stream input/output 45.Sh SYNOPSIS 46.Fd #include <stdio.h> 47.Ft size_t 48.Fn fread "void *ptr" "size_t size" "size_t nmemb" "FILE *stream" 49.Ft size_t 50.Fn fwrite "const void *ptr" "size_t size" "size_t nmemb" "FILE *stream" 51.Sh DESCRIPTION 52The function 53.Fn fread 54reads 55.Fa nmemb 56objects, each 57.Fa size 58bytes long, from the stream pointed to by 59.Fa stream , 60storing them at the location given by 61.Fa ptr . 62.Pp 63The function 64.Fn fwrite 65writes 66.Fa nmemb 67objects, each 68.Fa size 69bytes long, to the stream pointed to by 70.Fa stream , 71obtaining them from the location given by 72.Fa ptr . 73.Sh RETURN VALUES 74The functions 75.Fn fread 76and 77.Fn fwrite 78advance the file position indicator for the stream 79by the number of bytes read or written. 80They return the number of objects read or written. 81If an error occurs, or the end-of-file is reached, 82the return value is a short object count (or zero). 83.Pp 84The function 85.Fn fread 86does not distinguish between end-of-file and error, and callers 87must use 88.Xr feof 3 89and 90.Xr ferror 3 91to determine which occurred. 92The function 93.Fn fwrite 94returns a value less than 95.Fa nmemb 96only if a write error has occurred. 97.Sh SEE ALSO 98.Xr read 2 , 99.Xr write 2 100.Sh STANDARDS 101The functions 102.Fn fread 103and 104.Fn fwrite 105conform to 106.St -ansiC . 107