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 .