trusty (3) fwrite.3posix.gz

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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. Otherwise, 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-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
       ferror()  ,  fopen()  ,  printf()  ,  putc()  ,  puts()  ,  write()  ,  the  Base  Definitions  volume of
       IEEE Std 1003.1-2001, <stdio.h>


       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, 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 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 .