backq - get pointer to the queue behind the current queue
#include <sys/stream.h> queue_t *backq(queue_t *cq);
Architecture independent level 1 (DDI/DKI).
The pointer to the current queue. queue_t is an alias for the queue(9S) structure.
The backq() function 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.
If successful, backq() returns a pointer to the queue preceding the current queue. Otherwise, it returns NULL.
The backq() function can be called from user, interrupt, or kernel context.