SETBUF(3)                  POSIX Programmer's Manual                 SETBUF(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

NAME
       setbuf -- assign buffering to a stream

SYNOPSIS
       #include <stdio.h>

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

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.

       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.

RETURN VALUE
       The setbuf() function shall not return a value.

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

       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 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().

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       Section 2.5, Standard I/O Streams, fopen(), setvbuf()

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

COPYRIGHT
       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(3)
