setbuf(3S)                                                setbuf(3S)


       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
             setbuf may be used after a stream [see intro(3)] has been
             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.

             setbuf can also be used after a stream has been opened and
             written to if the buffer has been flushed with fflush prior to
             calling setbuf. [See fopen(3S)].  This will prevent loss of
             data in the existing buffer.

             To use setbuf after a read, make sure that the application has
             read all of the characters in one buffer and make sure that it
             will not receive any more characters until after calling
             setbuf.

             While there is no limitation on the size of the buffer, the
             constant BUFSIZ, defined in the stdio.h header file, is
             typically a good buffer size:

                   char buf[BUFSIZ];

             setvbuf may be used after a stream has been opened but before
             it is read or written.  type determines how stream will be
             buffered.  Valid values for type (defined in stdio.h) are:

             _IOFBF      causes input/output to be fully buffered.

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

             _IONBF      causes input/output to be completely unbuffered.

             If buf is not the NULL pointer, the array it points to is used
             for buffering, instead of an automatically allocated buffer.
             size specifies the size of the buffer to be used.  If


                           Copyright 1994 Novell, Inc.               Page 1

      setbuf(3S)                                                setbuf(3S)


            input/output is unbuffered, buf and size are ignored.

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

         Errors
            If an invalid value for type is provided, setvbuf returns a
            non-zero value.  Otherwise, it returns zero.

      REFERENCES
            fopen(3S), getc(3S), malloc(3C), putc(3S), stdio(3S)

      NOTICES
            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.

            Parts of buf are used for internal bookkeeping of the stream
            and, therefore, buf contains less than size bytes when full.
            It is recommended that the automatically allocated buffer is
            used when using setvbuf.




























                          Copyright 1994 Novell, Inc.               Page 2