opensolaris man page for setbuffer

setbuffer(3C)						   Standard C Library Functions 					     setbuffer(3C)

NAME
       setbuffer, setlinebuf - assign buffering to a stream

SYNOPSIS
       #include <stdio.h>

       void setbuffer(FILE *iop, char *abuf, size_t asize);

       int setlinebuf(FILE *iop);

DESCRIPTION
       The  setbuffer()  and  setlinebuf()  functions  assign  buffering to a stream. The three types of buffering available are unbuffered, block
       buffered, and line buffered. When an output stream is unbuffered, information appears on the destination file or terminal as soon as  writ-
       ten;  when  it  is  block  buffered, many characters are saved and written as a block; when it is line buffered, characters are saved until
       either a NEWLINE is encountered or input is read from stdin. The fflush(3C) function may be used to force the block out early. Normally all
       files  are  block buffered. A buffer is obtained from malloc(3C) upon the first getc(3C) or putc(3C) performed on the file. If the standard
       stream stdout refers to a terminal, it is line buffered. The standard stream stderr is unbuffered by default.

       The setbuffer() function can be used after a stream iop has been opened but before it is read or written. It uses the character array  abuf
       whose  size  is	determined  by the asize argument instead of an automatically allocated buffer.  If abuf is the null pointer, input/output
       will be completely unbuffered. A manifest constant BUFSIZ, defined in the <stdio.h> header, tells how large an array is needed:

       char buf[BUFSIZ];

       The setlinebuf() function is used to change the buffering on a stream from block buffered or  unbuffered  to  line  buffered.  Unlike  set-
       buffer(), it can be used at any time that the stream iop is active.

       A  stream  can  be  changed  from  unbuffered  or  line buffered to block buffered by using freopen(3C). A stream can be changed from block
       buffered or line buffered to unbuffered by using freopen(3C) followed by setbuf(3C) with a buffer argument of NULL.

RETURN VALUES
       The setlinebuf() function returns no useful value.

SEE ALSO
       malloc(3C), fclose(3C), fopen(3C), fread(3C), getc(3C), printf(3C), putc(3C), puts(3C), setbuf(3C), setvbuf(3C)

NOTES
       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.

SunOS 5.11							    13 May 1997 						     setbuffer(3C)