1FWRITE(3P)                 POSIX Programmer's Manual                FWRITE(3P)
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PROLOG

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

12       fwrite - binary output
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SYNOPSIS

15       #include <stdio.h>
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17       size_t fwrite(const void *restrict ptr, size_t size, size_t nitems,
18              FILE *restrict stream);
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DESCRIPTION

22       The fwrite() function shall write, from the array pointed to by ptr, up
23       to  nitems  elements  whose  size  is  specified by size, to the stream
24       pointed to by stream.  For each object, size calls shall be made to the
25       fputc()  function,  taking  the  values  (in  order)  from  an array of
26       unsigned char exactly overlaying the object. The file-position  indica‐
27       tor  for  the  stream  (if  defined) shall be advanced by the number of
28       bytes successfully written. If an error occurs, the resulting value  of
29       the file-position indicator for the stream is unspecified.
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31       The st_ctime and st_mtime fields of the file shall be marked for update
32       between the successful execution of fwrite() and  the  next  successful
33       completion  of  a call to fflush() or fclose() on the same stream, or a
34       call to exit() or abort().
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RETURN VALUE

37       The fwrite() function shall return the number of elements  successfully
38       written, which may be less than nitems if a write error is encountered.
39       If size or nitems is 0, fwrite() shall return 0 and the  state  of  the
40       stream remains unchanged. Otherwise, if a write error occurs, the error
41       indicator for the stream shall be set,  and errno shall be set to indi‐
42       cate the error.
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ERRORS

45       Refer to fputc().
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47       The following sections are informative.
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EXAMPLES

50       None.
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APPLICATION USAGE

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

59       None.
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FUTURE DIRECTIONS

62       None.
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SEE ALSO

65       ferror(), fopen(), printf(), putc(), puts(), write(), the Base  Defini‐
66       tions volume of IEEE Std 1003.1-2001, <stdio.h>
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69       Portions  of  this text are reprinted and reproduced in electronic form
70       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
71       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
72       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
73       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
74       event of any discrepancy between this version and the original IEEE and
75       The  Open Group Standard, the original IEEE and The Open Group Standard
76       is the referee document. The original Standard can be  obtained  online
77       at http://www.opengroup.org/unix/online.html .
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81IEEE/The Open Group                  2003                           FWRITE(3P)
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