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OPEN_MEMSTREAM(3)	   Linux Programmer's Manual	     OPEN_MEMSTREAM(3)

       open_memstream, open_wmemstream -  open a dynamic memory buffer stream

       #include <stdio.h>

       FILE *open_memstream(char **ptr, size_t *sizeloc);

       #include <wchar.h>

       FILE *open_wmemstream(wchar_t **ptr, size_t *sizeloc);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       open_memstream(), open_wmemstream():
	   Since glibc 2.10:
	       _POSIX_C_SOURCE >= 200809L
	   Before glibc 2.10:

       The  open_memstream()  function	opens a stream for writing to a memory
       buffer.	The function dynamically allocates the buffer, and the	buffer
       automatically  grows  as	 needed.   Initially, the buffer has a size of
       zero.  After closing the stream, the caller should free(3) this buffer.

       The locations pointed to by ptr and sizeloc are used to report, respec-
       tively, the current location and the size of the buffer.	 The locations
       referred to by these pointers are  updated  each	 time  the  stream  is
       flushed	(fflush(3))  and when the stream is closed (fclose(3)).	 These
       values remain valid only as long as the caller performs no further out-
       put  on	the  stream.   If further output is performed, then the stream
       must again be flushed before trying to access these values.

       A null byte is maintained at the end of the buffer.  This byte  is  not
       included in the size value stored at sizeloc.

       The  stream  maintains  the notion of a current position, which is ini-
       tially zero (the start of the buffer).  Each write operation implicitly
       adjusts	the  buffer  position.	 The  stream's	buffer position can be
       explicitly changed with fseek(3) or fseeko(3).  Moving the buffer posi-
       tion  past  the	end  of the data already written fills the intervening
       space with null characters.

       The open_wmemstream() is similar to open_memstream(), but  operates  on
       wide characters instead of bytes.

       Upon  successful	 completion,  open_memstream()	and  open_wmemstream()
       return a FILE pointer.  Otherwise, NULL is returned and errno is set to
       indicate the error.

       open_memstream()	 was  already  available  in  glibc 1.0.x.  open_wmem-
       stream() is available since glibc 2.4.

       For  an	explanation  of	 the  terms  used   in	 this	section,   see

       |Interface	  | Attribute	  | Value   |
       |open_memstream(), | Thread safety | MT-Safe |
       |open_wmemstream	  |		  |	    |

       POSIX.1-2008.   These  functions are not specified in POSIX.1-2001, and
       are not widely available on other systems.

       There is no file descriptor associated with the file stream returned by
       these  functions (i.e., fileno(3) will return an error if called on the
       returned stream).

       In glibc before version 2.7, seeking past the end of a  stream  created
       by  open_memstream()  does not enlarge the buffer; instead the fseek(3)
       call fails, returning -1.

       See fmemopen(3).

       fmemopen(3), fopen(3), setbuf(3)

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GNU				  2016-03-15		     OPEN_MEMSTREAM(3)