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FREAD(3P)                  POSIX Programmer's Manual                 FREAD(3P)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may dif-
       fer (consult the corresponding Linux manual page for details of Linux behavior), or the interface  may  not  be
       implemented on Linux.

NAME
       fread - binary input

SYNOPSIS
       #include <stdio.h>

       size_t fread(void *restrict ptr, size_t size, size_t nitems,
              FILE *restrict stream);


DESCRIPTION
       The  fread() function shall read into the array pointed to by ptr up to nitems elements whose size is specified
       by size in bytes, from the stream pointed to by stream.  For each object, size  calls  shall  be  made  to  the
       fgetc() function and the results stored, in the order read, in an array of unsigned char exactly overlaying the
       object. The file position indicator for the stream (if defined) shall be advanced by the number of  bytes  suc-
       cessfully  read.  If  an  error  occurs,  the  resulting value of the file position indicator for the stream is
       unspecified. If a partial element is read, its value is unspecified.

       The fread() function may mark the st_atime field of the file associated with stream for  update.  The  st_atime
       field  shall  be  marked  for update by the first successful execution of fgetc(), fgets(), fgetwc(), fgetws(),
       fread(), fscanf(), getc(), getchar(), gets(), or scanf() using stream that returns data not supplied by a prior
       call to ungetc() or ungetwc().

RETURN VALUE
       Upon  successful  completion,  fread() shall return the number of elements successfully read which is less than
       nitems only if a read error or end-of-file is encountered. If size or nitems is 0, fread() shall return  0  and
       the  contents of the array and the state of the stream remain unchanged. Otherwise, if a read error occurs, the
       error indicator for the stream shall be set,  and errno shall be set to indicate the error.

ERRORS
       Refer to fgetc().

       The following sections are informative.

EXAMPLES
   Reading from a Stream
       The following example reads a single element from the fp stream into the array pointed to by buf.


              #include <stdio.h>
              ...
              size_t bytes_read;
              char buf[100];
              FILE *fp;
              ...
              bytes_read = fread(buf, sizeof(buf), 1, fp);
              ...

APPLICATION USAGE
       The ferror() or feof() functions must be used to distinguish between an error condition and an end-of-file con-
       dition.

       Because  of possible differences in element length and byte ordering, files written using fwrite() are applica-
       tion-dependent, and possibly cannot be read using fread() by a different application or by the same application
       on a different processor.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       feof(),   ferror(),   fgetc(),   fopen(),   getc(),   gets(),   scanf(),   the   Base   Definitions  volume  of
       IEEE Std 1003.1-2001, <stdio.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Stan-
       dard  for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifica-
       tions Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,  Inc  and  The
       Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Stan-
       dard, the original IEEE and The Open Group Standard is the referee  document.  The  original  Standard  can  be
       obtained online at http://www.opengroup.org/unix/online.html .



IEEE/The Open Group                  2003                            FREAD(3P)