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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 .