SETBUF(3S)           INTERACTIVE UNIX System           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;

          DESCRIPTION
               The setbuf function may be used after a stream has been
               opened but before it is read or written.  It causes the
               array pointed to by buf to be used instead of an automati-
               cally allocated buffer.  If buf 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];

               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.
               The constant BUFSIZ in <stdio.h> is suggested as a good
               buffer size.  If input/output is unbuffered, buf and size
               are ignored.

               By default, output to a terminal is line-buffered and all
               other input/output is fully buffered.

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



          Rev. C Software Development Set                            Page 1

          SETBUF(3S)           INTERACTIVE UNIX System           SETBUF(3S)



          DIAGNOSTICS
               If an illegal value for type or size is provided, setvbuf
               returns a non-zero value. Otherwise, the value returned will
               be 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.














































          Rev. C Software Development Set                            Page 2