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FWRITE(3P)                 POSIX Programmer's Manual                FWRITE(3P)
PROLOG
       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.
NAME
       fwrite -- binary output
SYNOPSIS
       #include <stdio.h>
       size_t fwrite(const void *restrict ptr, size_t size, size_t nitems,
           FILE *restrict stream);
DESCRIPTION
       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.1-2008
       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
       unsigned  char exactly overlaying the object. The file-position indica-
       tor 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().
RETURN VALUE
       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 indi-
       cate the error.
ERRORS
       Refer to fputc().
       The following sections are informative.
EXAMPLES
       None.
APPLICATION USAGE
       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.
RATIONALE
       None.
FUTURE DIRECTIONS
       None.
SEE ALSO
       Section  2.5,  Standard  I/O  Streams,  ferror(),  fopen(),  fprintf(),
       putc(), puts(), write()
       The Base Definitions volume of POSIX.1-2008, <stdio.h>
COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal and Electronics Engineers,  Inc  and  The  Open  Group.   (This  is
       POSIX.1-2008  with  the  2013  Technical Corrigendum 1 applied.) 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.unix.org/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.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                           FWRITE(3P)