backq(9F)

NAME

     backq - get pointer to the queue behind the current queue

SYNOPSIS

     #include <sys/stream.h>

     queue_t *backq(queue_t *cq);

INTERFACE LEVEL

     Architecture independent level 1 (DDI/DKI).

PARAMETERS

     cq    The pointer to the  current  queue.    queue_t  is  an
           alias for the queue(9S) structure.

DESCRIPTION

     backq() returns a pointer to the queue  preceding   cq  (the
     current  queue).  If  cq is a read queue,  backq() returns a
     pointer to the queue downstream from  cq, unless it  is  the
     stream  end.  If   cq  is  a write queue,  backq() returns a
     pointer to the next queue upstream from  cq,  unless  it  is
     the stream head.

RETURN VALUES

     If successful,  backq()  returns  a  pointer  to  the  queue
     preceding the current queue.  Otherwise, it returns  NULL.

CONTEXT

     backq() can be called from user or interrupt context.

SEE ALSO

     queue(9S)

     Writing Device Drivers

     STREAMS Programming Guide