#include <stdlib.h> void insque(struct qelem *elem, struct qelem *prev); void remque(struct qelem *elem);
The qelem structure is defined as
struct qelem { struct qelem *q_forw; struct qelem *q_back; char q_data[1]; };
insque() inserts the element pointed to by elem immediately after the element pointed to by prev, which must NOT be NULL.
remque() removes the element pointed to by elem from the doubly-linked list.
The location of the prototypes for these functions differ among several versions of UNIX. Some systems place them in <search.h>, others in <string.h>. Linux places them in <stdlib.h> since that seems to make the most sense.
Some versions of UNIX (like HP-UX 10.x) do not define a struct qelem but rather have the arguments to insque() and remque() be of type void *.