SETVBUF(P) POSIX Programmer's Manual SETVBUF(P)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.
NAMEsetvbuf - assign buffering to a stream
SYNOPSIS
#include <stdio.h>
int setvbuf(FILE *restrict stream, char *restrict buf, int type,
size_t size);
DESCRIPTION
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 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
Standard I/O Streams , fopen() , setbuf() , the Base Definitions volume
of IEEE Std 1003.1-2001, <stdio.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 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 .
IEEE/The Open Group 2003 SETVBUF(P)
