runnable tail queue code

Make the tail queue sample in man page work.

 

#include <sys/queue.h>
#include <stdlib.h>
#include <stdio.h>

int main(int argc, const char *argv[]) 
{
    TAILQ_HEAD(tailhead, entry) head;
    struct tailhead *headp;
    headp = &head;

    struct entry {
        int val;
        TAILQ_ENTRY(entry) entries;
    } *n1, *n2, *np;

    TAILQ_INIT(headp);

    n1 = malloc(sizeof(struct entry));
    n1->val = 10;
    TAILQ_INSERT_HEAD(headp, n1, entries);

    n1 = malloc(sizeof(struct entry));
    n1->val = 100;
    TAILQ_INSERT_TAIL(headp, n1, entries);

    n2 = malloc(sizeof(struct entry));
    n2->val = 200;
    TAILQ_INSERT_AFTER(headp, n1, n2, entries);

    for (np = headp->tqh_first; np != NULL; np = np->entries.tqe_next)
        printf("value: %d\n", np->val);

    while (headp->tqh_first != NULL)
        TAILQ_REMOVE(headp, headp->tqh_first, entries);
    return 0;
}