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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 (consult 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 argument size speci-
       fies 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 .

IEEE/The Open Group                  2003                          SETVBUF(3P)