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 argument 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 buffer 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, 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 .