/*
 * Copyright (c) 1990, 2010, Oracle and/or its affiliates. All rights reserved.
 */

/*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/*        All Rights Reserved   */

/*
 * Copyright (c) 1980 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 */

/*
 * users
 */

#include <stdio.h>
#include <sys/types.h>
#include <stdlib.h>
#include <utmpx.h>
#include <string.h>

static char **names;
static char **namp;

static int scmp(const void *p, const void *q);
static void summary(void);

int
main(int argc, char **argv)
{
        int     nusers = 0;
        int     bufflen = BUFSIZ;
        struct utmpx *utmpx;

        if (argc == 2)
                if (!utmpxname(argv[1])) {
                        (void) fprintf(stderr, "Filename is too long\n");
                        exit(1);
                }

        names = namp = (char **)realloc((void *)NULL, BUFSIZ * sizeof (char *));

        setutxent();

        while ((utmpx = getutxent()) != NULL) {
                if (utmpx->ut_name[0] == '\0')
                        continue;
                if (utmpx->ut_type != USER_PROCESS)
                        continue;
                if (nonuserx(*utmpx))
                        continue;
                if (nusers == bufflen) {
                        bufflen *= 2;
                        names = (char **)realloc(names,
                            bufflen * sizeof (char *));
                        namp = names + nusers;
                }
                *namp++ = strndup(utmpx->ut_name, sizeof (utmpx->ut_name));
                nusers++;
        }

        endutxent();

        summary();
        return (0);
}

static int
scmp(const void *p, const void *q)
{
        return (strcmp((char *)p, (char *)q));
}

static void
summary(void)
{
        register char **p;

        qsort(names, namp - names, sizeof (names[0]), scmp);
        for (p = names; p < namp; p++) {
                if (p != names)
                        (void) putchar(' ');
                (void) fputs(*p, stdout);
        }
        if (namp != names)              /* at least one user */
                (void) putchar('\n');
}