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FDOPEN(P)		   POSIX Programmer's Manual		     FDOPEN(P)

NAME
       fdopen - associate a stream with a file descriptor

SYNOPSIS
       #include <stdio.h>

       FILE *fdopen(int fildes, const char *mode);

DESCRIPTION
       The fdopen() function shall associate a stream with a file descriptor.

       The  mode  argument  is	a character string having one of the following
       values:

       r or rb
	      Open a file for reading.

       w or wb
	      Open a file for writing.

       a or ab
	      Open a file for writing at end-of-file.

       r+ or rb+ or r+b
	      Open a file for update (reading and writing).

       w+ or wb+ or w+b
	      Open a file for update (reading and writing).

       a+ or ab+ or a+b
	      Open a file for update (reading and writing) at end-of-file.

       The meaning of these flags is exactly as specified in  fopen(),	except
       that modes beginning with w shall not cause truncation of the file.

       Additional  values  for the mode argument may be supported by an imple‐
       mentation.

       The application shall ensure that the mode of the stream	 as  expressed
       by  the	mode  argument	is allowed by the file access mode of the open
       file description to which fildes refers. The  file  position  indicator
       associated  with the new stream is set to the position indicated by the
       file offset associated with the file descriptor.

       The error and end-of-file indicators for the stream shall  be  cleared.
       The  fdopen()  function	may cause the st_atime field of the underlying
       file to be marked for update.

       If fildes refers to a shared memory object, the result of the  fdopen()
       function is unspecified.

       If  fildes  refers to a typed memory object, the result of the fdopen()
       function is unspecified.

       The fdopen() function shall preserve the offset maximum previously  set
       for the open file description corresponding to fildes.

RETURN VALUE
       Upon  successful	 completion,  fdopen()	shall  return  a  pointer to a
       stream; otherwise, a null pointer shall be returned and	errno  set  to
       indicate the error.

ERRORS
       The fdopen() function may fail if:

       EBADF  The fildes argument is not a valid file descriptor.

       EINVAL The mode argument is not a valid mode.

       EMFILE {FOPEN_MAX} streams are currently open in the calling process.

       EMFILE {STREAM_MAX} streams are currently open in the calling process.

       ENOMEM Insufficient space to allocate a buffer.

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       File  descriptors  are obtained from calls like open(), dup(), creat(),
       or pipe(), which open files but do not return streams.

RATIONALE
       The file descriptor  may	 have  been  obtained  from  open(),  creat(),
       pipe(), dup(), or fcntl(); inherited through fork() or exec; or perhaps
       obtained by implementation-defined means, such as the 4.3 BSD  socket()
       call.

       The  meanings  of  the  mode  arguments of fdopen() and fopen() differ.
       With fdopen(), open for write (w or w+) does not truncate,  and	append
       (a  or  a+)  cannot  create for writing. The mode argument formats that
       include a b are allowed for consistency with the ISO C  standard	 func‐
       tion fopen(). The b has no effect on the resulting stream. Although not
       explicitly required by this  volume  of	IEEE Std 1003.1-2001,  a  good
       implementation  of  append (a) mode would cause the O_APPEND flag to be
       set.

FUTURE DIRECTIONS
       None.

SEE ALSO
       Interaction of File Descriptors and Standard I/O Streams ,  fclose()  ,
       fopen() , open() , 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,  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 .

IEEE/The Open Group		     2003			     FDOPEN(P)
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