This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

       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.

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for  Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       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.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                                       SETVBUF(3POSIX)

       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.1‐2017 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 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 Section2.5, StandardI/OStreams.

       The setvbuf() function may fail if:

       EBADF  The file descriptor underlying stream is not valid.

       Thefollowingsectionsareinformative.

       None.

       None.

       setvbuf — assign buffering to a stream

       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.

       None.

       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.

Section2.5, StandardI/OStreams, fopen(), setbuf()

       The Base Definitions volume of POSIX.1‐2017, <stdio.h>

       #include <stdio.h>

       int setvbuf(FILE *restrict stream, char *restrict buf, int type,
           size_t size);