setbuf(3C)						   Standard C Library Functions 						setbuf(3C)

NAME

       setbuf, setvbuf - assign buffering to a stream

SYNOPSIS

       #include <stdio.h>

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

       int setvbuf(FILE *stream, char *buf, int type, size_t size);

DESCRIPTION

       The  setbuf()  function	may  be  used  after the stream pointed to by stream (see Intro(3)) is opened but before it is read or written. It
       causes the array pointed to by buf to be used instead of an automatically allocated buffer. If buf is the null pointer,	input/output  will
       be completely unbuffered.  The constant	BUFSIZ, defined in the <stdio.h> header, indicates the size of the array pointed to by buf.

       The  setvbuf()  function  may be used after a stream is opened  but before it is read or written.  The type argument determines how  stream
       will be buffered. Legal values for  type (defined in <stdio.h>) are:

       _IOFBF	 Input/output to be fully buffered.

       _IOLBF	 Output to be line buffered;  the buffer will be flushed when a NEWLINE is written, the buffer is full, or input is requested.

       _IONBF	 Input/output to be completely unbuffered.

       If buf is not the null pointer, the array it points to will be used for buffering, instead of an automatically allocated buffer.  The  size
       argument specifies the size of the buffer to be used. If input/output is unbuffered,  buf and  size are ignored.

       For a further discussion of buffering, see stdio(3C).

RETURN VALUES

       If an illegal value for	type is provided, setvbuf() returns a non-zero value.	Otherwise, it returns 0.

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.

       When using setbuf(), buf should always be sized using BUFSIZ. If the array pointed to by buf is larger than BUFSIZ, a portion of  buf  will
       not be used.  If buf is smaller than BUFSIZ, other memory may be unexpectedly overwritten.

       Parts  of  buf  will  be used for internal bookkeeping of the stream and, therefore, buf will contain less than size bytes when full. It is
       recommended that  stdio(3C) be used to handle buffer allocation when using setvbuf().

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       fopen(3C), getc(3C), malloc(3C), putc(3C), stdio(3C), attributes(5), standards(5)

SunOS 5.11							    14 Aug 2002 							setbuf(3C)