SETBUF(3S)          UNIX Programmer's Manual           SETBUF(3S)

NAME
     setbuf, setvbuf - assign buffering to a stream

SYNOPSIS
     #include <stdio.h>

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

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

COMPATIBILITY
     Level:    HP-UX/RUN ONLY

     Origin:   System III

DESCRIPTION
     _S_e_t_b_u_f may be used after a stream has been opened but before
     it  is  read  or written.  It causes the array pointed to by
     _b_u_f to be used instead of an automatically allocated buffer.
     If  _b_u_f  is the NULL pointer input/output will be completely
     unbuffered.

     A constant BUFSIZ, defined in  the  <stdio.h>  header  file,
     tells how big an array is needed:

          char buf[BUFSIZ];
     _S_e_t_v_b_u_f may be used after  a  stream  has  been  opened  but
     before  it  is  read or written.  _T_y_p_e determines how _s_t_r_e_a_m
     will  be  buffered.   Legal  values  for  _t_y_p_e  (defined  in
     stdio.h) are:

     _IOFBF  causes input/output to be fully buffered.

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

     _IONBF  causes input/output to be completely unbuffered.  If
             _b_u_f  is not the NULL pointer, the array it points to
             will be used for buffering, instead of an  automati-
             cally  allocated buffer.  _S_i_z_e specifies the size of
             the buffer to  be  used.   The  constant  BUFSIZ  in
             <stdio.h>  is  suggested  as a good buffer size.  If
             input/output  is  unbuffered,  _b_u_f  and   _s_i_z_e   are
             ignored.   By  default, output to a terminal is line
             buffered and all other input/output  is  fully  buf-
             fered.

SEE ALSO
     fopen(3S), getc(3S), malloc(3C), putc(3S), stdio(3S).

DIAGNOSTICS
     If an illegal value for _t_y_p_e or _s_i_z_e is provided, or alloca-
     tion fails when bug==NULL, _s_e_t_v_b_u_f returns a non-zero value.
     Otherwise, the value returned will be zero.

NOTE
     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.