plucky (3) setvbuf.3posix.gz

Provided by: manpages-posix-dev_2017a-2_all bug

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.1‐2017 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 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.1‐2017, <stdio.h>


       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 .