#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <time.h>
#include <utmp.h>

struct utmplist {
        struct utmplist *next;
        struct utmp     u;
};

struct utmplist *read_utmp(FILE *fp, struct utmplist *head)
{
        struct utmplist *ulprev, *ulp;

        for (;;) {
                ulp = calloc(1, sizeof(struct utmplist));
                if (ulp == NULL) {
                        perror("calloc");
                        fclose(fp);
                        exit(-1);
                }

                if (fread(&ulp->u, sizeof(ulp->u), 1, fp) != 1) {
                        free(ulp);
                        break;
                }

                if (head == NULL) {
                        head = ulp;
                } else {
                        ulprev->next = ulp;
                }

                ulprev = ulp;
        }

        return head;
}

void write_utmp(FILE *fp, struct utmplist *head)
{
        struct utmplist *ulprev;
        struct utmplist *ulp = head;

        while (ulp) {
                if (ulp->u.ut_type != DEAD_PROCESS) {
                        time_t t = ulp->u.ut_time;
                        printf("%8.8s|%16.16s|%8.8s|%s", ulp->u.ut_name,
                               ulp->u.ut_host, ulp->u.ut_line, ctime(&t));
                }
                ulprev = ulp;
                ulp = ulp->next;
                free(ulprev);
        }
}

int main(void)
{
        FILE *fp;
        struct utmplist *ulhead = NULL;

        fp = fopen(_PATH_UTMP, "r");
        if (fp == NULL) {
                perror(_PATH_UTMP);
                exit(-1);
        }

        ulhead = read_utmp(fp, ulhead);

        fclose(fp);

        write_utmp(stdout, ulhead);

        return 0;
}