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  setbuf(),  allocating  a buffer of BUFSIZ bytes does not necessarily imply that all of BUFSIZ bytes
       are used for the buffer area.

       Since errno is not required to be unchanged on success, in order to correctly detect and possibly recover
       from errors, applications should use setvbuf() instead of setbuf().

       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                                        SETBUF(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.

       Except that it returns no value, the function call:

           setbuf(stream, buf)

       shall be equivalent to:

           setvbuf(stream, buf, _IOFBF, BUFSIZ)

       if buf is not a null pointer, or to:

           setvbuf(stream, buf, _IONBF, BUFSIZ)

       if buf is a null pointer.

       Although  the  setvbuf()  interface  may  set  errno  in defined ways, the value of errno after a call to
       setbuf() is unspecified.

       Thefollowingsectionsareinformative.

       None.

       None.

       setbuf — 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.

       The setbuf() function shall not return a value.

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

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

       #include <stdio.h>

       void setbuf(FILE *restrict stream, char *restrict buf);