HP C/iX Library Reference Manual (30026-90004)

Chapter 5 309
HP C/iX Library Function Descriptions
setvbuf
setvbuf
Assigns a buffer and buffering method to an open stream.
Syntax
#include <stdio.h>
int setvbuf (FILE * stream , char * buffer ,
int type , size_t size );
Parameters
stream A pointer to an open stream.
buffer Either a pointer to a character array for buffered I/O, or null.
type The method of buffering.
size The size of the buffer.
Return Values
0 Success.
≠0 An error occurred.
Description
The setvbuf function enables you to assign a character array for buffering, and also
provides the means to specify the size of the buffer to be used (
size ) and the type of
buffering to be done (
type ). Acceptable values for type (defined in <stdio.h>) include:
_IOFBF Input/output is fully buffered.
_IOLBF Output is line buffered. The buffer is flushed each time a new line is
written, the buffer is full, or input is requested.
_IONBF Input/output is completely unbuffered.
If
type _IONBF is specified, stream is totally unbuffered. Because no buffer is needed,
values for
buffer and size are ignored.
If
buffer is the null pointer and type is specified as _IOFBF or _IOLBF, setvbuf()
automatically allocates a buffer of
size bytes through a call to malloc().
If
size is zero, a buffer of size BUFSIZ is used. This behavior can be used to change the
buffer size for a stream even if you still want the standard I/O system to automatically
allocate the buffer. This is particularly useful when a buffer larger than the specified
BUFSIZ is needed.
Examples
In the following examples, the following two calls, though different, are functionally