stdio/FreeBSD/fread.3

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  36 .\"     @(#)fread.3     8.2 (Berkeley) 3/8/94
  37 .\" $FreeBSD: src/lib/libc/stdio/fread.3,v 1.9 2002/10/12 16:13:37 mike Exp $
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  39 .Dd March 8, 1994
  40 .Dt FREAD 3
  41 .Os
  42 .Sh NAME
  43 .Nm fread ,
  44 .Nm fwrite
  45 .Nd binary stream input/output
  46 .Sh LIBRARY
  47 .Lb libc
  48 .Sh SYNOPSIS
  49 .In stdio.h
  50 .Ft size_t
  51 .Fn fread "void * restrict ptr" "size_t size" "size_t nmemb" "FILE * restrict stream"
  52 .Ft size_t
  53 .Fn fwrite "const void * restrict ptr" "size_t size" "size_t nmemb" "FILE * restrict stream"
  54 .Sh DESCRIPTION
  55 The function
  56 .Fn fread
  57 reads
  58 .Fa nmemb
  59 objects, each
  60 .Fa size
  61 bytes long, from the stream pointed to by
  62 .Fa stream ,
  63 storing them at the location given by
  64 .Fa ptr .
  65 .Pp
  66 The function
  67 .Fn fwrite
  68 writes
  69 .Fa nmemb
  70 objects, each
  71 .Fa size
  72 bytes long, to the stream pointed to by
  73 .Fa stream ,
  74 obtaining them from the location given by
  75 .Fa ptr .
  76 .Sh RETURN VALUES
  77 The functions
  78 .Fn fread
  79 and
  80 .Fn fwrite
  81 advance the file position indicator for the stream
  82 by the number of bytes read or written.
  83 They return the number of objects read or written.
  84 If an error occurs, or the end-of-file is reached,
  85 the return value is a short object count (or zero).
  86 .Pp
  87 The function
  88 .Fn fread
  89 does not distinguish between end-of-file and error, and callers
  90 must use
  91 .Xr feof 3
  92 and
  93 .Xr ferror 3
  94 to determine which occurred.
  95 The function
  96 .Fn fwrite
  97 returns a value less than
  98 .Fa nmemb
  99 only if a write error has occurred.
 100 .Sh SEE ALSO
 101 .Xr read 2 ,
 102 .Xr write 2
 103 .Sh STANDARDS
 104 The functions
 105 .Fn fread
 106 and
 107 .Fn fwrite
 108 conform to
 109 .St -isoC .