v7 man page for setbuf

SETBUF(3S)																SETBUF(3S)

NAME
       setbuf - assign buffering to a stream

SYNOPSIS
       #include <stdio.h>

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

DESCRIPTION
       Setbuf is used after a stream has been opened but before it is read or written.	It causes the character array buf to be used instead of an
       automatically allocated buffer.	If buf is the constant pointer NULL, input/output will be completely unbuffered.

       A manifest constant BUFSIZ tells how big an array is needed:

		 char buf[BUFSIZ];

       A buffer is normally obtained from malloc(3) upon the first getc or putc(3) on the file, except that output streams directed to	terminals,
       and the standard error stream stderr are normally not buffered.

SEE ALSO
       fopen(3), getc(3), putc(3), malloc(3)

																	SETBUF(3S)