@node setvbuf, stdio
@subheading Syntax

@example
#include <stdio.h>

int setvbuf(FILE *file, char *buffer, int type, int length);
@end example

@subheading Description

This function modifies the buffering characteristics of @var{file}. 
First, if the file already has a buffer, it is freed.  If there was any
pending data in it, it is lost, so this function should only be used
immediately after a call to @code{fopen}.

If the @var{type} is @code{_IONBF}, the @var{buffer} and @var{length}
are ignored and the file is set to unbuffered mode. 

If the @var{type} is @code{_IOLBF} or @code{_IOFBF}, then the file is
set to line or fully buffered, respectively.  If @var{buffer} is
@code{NULL}, a buffer of size @var{size} is created and used as the
buffer.  If @var{buffer} is non-@code{NULL}, it must point to a buffer
of at least size @var{size} and will be used as the buffer. 

@xref{setbuf}.
@xref{setbuffer}.
@xref{setlinebuf}.

@subheading Return Value

Zero on success, nonzero on failure.

@subheading Portability

@portability ansi, posix

@subheading Example

@example
setvbuf(stderr, NULL, _IOLBF, 1000);
@end example