SETVBUF(3P)                                         POSIX Programmer's Manual                                        SETVBUF(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
       setvbuf - assign buffering to a stream

SYNOPSIS
       #include <stdio.h>

       int setvbuf(FILE *restrict stream, char *restrict buf, int type,
              size_t size);


DESCRIPTION
       The  setvbuf()  function may be used after the stream pointed to by stream is associated with an open file but before any
       other operation (other than an unsuccessful call to setvbuf()) is performed on the stream. The argument  type  determines
       how stream shall be buffered, as follows:

        * {_IOFBF} shall cause input/output to be fully buffered.

        * {_IOLBF} shall cause input/output to be line buffered.

        * {_IONBF} shall cause input/output to be unbuffered.

       If buf is not a null pointer, the array it points to may be used instead of a buffer allocated by setvbuf() and the argu-
       ment size specifies the size of the array; otherwise, size may determine the size of a buffer allocated by the  setvbuf()
       function. The contents of the array at any time are unspecified.

       For information about streams, see Standard I/O Streams .

RETURN VALUE
       Upon  successful completion, setvbuf() shall return 0. Otherwise, it shall return a non-zero value if an invalid value is
       given for type or if the request cannot be honored,  and may set errno to indicate the error.

ERRORS
       The setvbuf() function may fail if:

       EBADF  The file descriptor underlying stream is not valid.


       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       A common source of error is allocating buffer space as an "automatic" variable in a code block, and then failing to close
       the stream in the same block.

       With setvbuf(), allocating a buffer of size bytes does not necessarily imply that all of size bytes are used for the buf-
       fer area.

       Applications should note that many implementations only provide line buffering on input from terminal devices.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       Standard I/O Streams, fopen(), setbuf(), 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                                                   SETVBUF(3P)