setbuffer(3S)        STANDARD I/O FUNCTIONS         setbuffer(3S)



NAME
     setbuffer, setlinebuf - assign buffering to a stream

SYNOPSIS
     cc [ flag... ] file ... -lucb
     #include <stdio.h>
     setbuffer(stream, buf, size)
     FILE *stream;
     char *buf;
     int size;
     setlinebuf(stream)
     FILE *stream;

DESCRIPTION
     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 written; when it is block buffered many
     characters are saved up and written as a block; when  it  is
     line  buffered  characters  are  saved up until a NEWLINE is
     encountered or input is read from any  line  buffered  input
     stream.   fflush  (see  fclose(3S)) 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 or
     putc(3S) on the file.  By default, output to a  terminal  is
     line  buffered,  except  for  output  to the standard stream
     stderr which is unbuffered, and all  other  input/output  is
     fully  buffered.   setbuffer  can be used after a stream has
     been opened but before it is read or written.  It  uses  the
     character  array  buf  whose  size is determined by the size
     argument instead of an automatically allocated  buffer.   If
     buf  is  the  NULL  pointer, input/output will be completely
     unbuffered.  A manifest  constant  BUFSIZ,  defined  in  the
     <stdio.h> header file, tells how big an array is needed:

          char buf[BUFSIZ]; setlinebuf  is  used  to  change  the
          buffering on a stream from block buffered or unbuffered
          to line buffered.  Unlike setbuffer, it can be used  at
          any  time  that  the file descriptor is active.  A file
          can be changed from  unbuffered  or  line  buffered  to
          block  buffered  by  using  freopen (see fopen(3S)).  A
          file can be changed from block buffered  or  line  buf-
          fered  to  unbuffered by using freopen followed by set-
          buffer with a buffer argument of NULL.

SEE ALSO
     setbuf(3S)  fclose(3S),  fopen(3S),   fread(3S),   getc(3S),
     malloc(3C),  printf(3S),  putc(3S),  puts(3S), setbuf(3S) in
     the Programmer's Reference Manual.

NOTE
     A common source of error is allocating buffer  space  as  an



             Last change: BSD Compatibility Package             1

setbuffer(3S)        STANDARD I/O FUNCTIONS         setbuffer(3S)



     automatic  variable  in  a  code  block, and then failing to
     close the stream in the same block.





















































             Last change: BSD Compatibility Package             2