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 (con-
       sult 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  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 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  st_ctime and st_mtime fields 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. Oth-
       erwise, if a write error occurs, the error indicator for the stream shall be set,  and errno shall be set to indicate 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-depen-
       dent, and possibly cannot be read using fread() by a different application or by the same application on a different pro-
       cessor.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       ferror(), fopen(), printf(), putc(), puts(), write(), 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, Standard for
       Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6,  Copy-
       right (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 Standard, the original IEEE and The Open  Group
       Standard   is   the   referee   document.   The   original   Standard   can   be   obtained  online  at  http://www.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                    FWRITE(3P)