setbuf(3S)                     DG/UX 5.4R3.00                     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, sizet 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.

       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.  Legal
       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 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 buf is not the NULL pointer, the array it points to will be used
       for buffering, instead of an automatically allocated buffer.  size
       specifies the size of the buffer to be used.  If input/output is
       unbuffered, buf and size are ignored.

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

   Considerations for Threads Programming
                     +---------+-----------------------------+
                     |         |                      async- |
                     |function | reentrant   cancel   cancel |
                     |         |              point    safe  |
                     +---------+-----------------------------+
                     |setbuf   |     Y          N        N   |
                     |setvbuf  |     Y          N        N   |
                     +---------+-----------------------------+
SEE ALSO
       reentrant(3), flockfile(3S), fopen(3S), getc(3S), malloc(3C),
       putc(3S), stdio(3S).




Licensed material--property of copyright holder(s)                         1

setbuf(3S)                     DG/UX 5.4R3.00                     setbuf(3S)


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

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.

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












































Licensed material--property of copyright holder(s)                         2