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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 functionality described on this reference page is aligned with  the
       ISO C  standard.  Any  conflict between the requirements described here
       and the ISO C standard is unintentional. This  volume  of  POSIX.1-2008
       defers to the ISO C standard.
       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 Section 2.5, 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
       Section 2.5, Standard I/O Streams, fopen(), setbuf()
       The Base Definitions volume of POSIX.1-2008, <stdio.h>
COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal and Electronics Engineers,  Inc  and  The  Open  Group.   (This  is
       POSIX.1-2008  with  the  2013  Technical Corrigendum 1 applied.) 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.unix.org/online.html .
       Any  typographical  or  formatting  errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files  to  man page format. To report such errors, see https://www.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                          SETVBUF(3P)