This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

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

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for  Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 Standard, 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 .

       Any typographical or formatting errors that appear in this page are most likely to have  been  introduced
       during   the   conversion  of  the  source  files  to  man  page  format.  To  report  such  errors,  see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                                        FWRITE(3POSIX)

       The  functionality  described  on  this  reference  page is aligned with the ISO C standard. Any conflict
       between the requirements described  here  and  the  ISO C  standard  is  unintentional.  This  volume  of
       POSIX.1‐2017 defers to the ISO C standard.

       The  fwrite() function shall write, from the array pointed to by ptr, up to nitems elements whose size is
       specified by size, to the stream pointed to by stream.  For each object, size calls shall be made to  the
       fputc()  function,  taking  the  values  (in order) from an array of unsignedchar exactly overlaying the
       object. The file-position indicator for the stream (if defined) shall be advanced by the number of  bytes
       successfully  written.  If  an  error  occurs, the resulting value of the file-position indicator for the
       stream is unspecified.

       The last data modification and last file status change timestamps of the file shall be marked for  update
       between  the successful execution of fwrite() and the next successful completion of a call to fflush() or
       fclose() on the same stream, or a call to exit() or abort().

       Refer to fputc().

       Thefollowingsectionsareinformative.

       None.

       None.

       fwrite — binary output

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

       None.

       The fwrite() function shall return the number of elements successfully written, which may  be  less  than
       nitems  if a write error is encountered. If size or nitems is 0, fwrite() shall return 0 and the state of
       the stream remains unchanged. Otherwise, if a write error occurs, the  error  indicator  for  the  stream
       shall be set, and errno shall be set to indicate the error.

Section2.5, StandardI/OStreams, ferror(), fopen(), fprintf(), putc(), puts(), write()

       The Base Definitions volume of POSIX.1‐2017, <stdio.h>

       #include <stdio.h>

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