source: MondoRescue/branches/3.2/mindi-busybox/miscutils/last.c@ 3232

/* vi: set sw=4 ts=4: */
/*
 * last implementation for busybox
 *
 * Copyright (C) 2003-2004 by Erik Andersen <andersen@codepoet.org>
 *
 * Licensed under GPLv2, see file LICENSE in this source tree.
 */

//usage:#define last_trivial_usage
//usage:       ""IF_FEATURE_LAST_FANCY("[-HW] [-f FILE]")
//usage:#define last_full_usage "\n\n"
//usage:       "Show listing of the last users that logged into the system"
//usage:    IF_FEATURE_LAST_FANCY( "\n"
/* //usage:  "\n    -H  Show header line" */
//usage:     "\n    -W  Display with no host column truncation"
//usage:     "\n    -f FILE Read from FILE instead of /var/log/wtmp"
//usage:    )

#include "libbb.h"

/* NB: ut_name and ut_user are the same field, use only one name (ut_user)
 * to reduce confusion */

#ifndef SHUTDOWN_TIME
#  define SHUTDOWN_TIME 254
#endif

/* Grr... utmp char[] members do not have to be nul-terminated.
 * Do what we can while still keeping this reasonably small.
 * Note: We are assuming the ut_id[] size is fixed at 4. */

#if defined UT_LINESIZE \
    && ((UT_LINESIZE != 32) || (UT_NAMESIZE != 32) || (UT_HOSTSIZE != 256))
#error struct utmp member char[] size(s) have changed!
#elif defined __UT_LINESIZE \
    && ((__UT_LINESIZE != 32) || (__UT_NAMESIZE != 64) || (__UT_HOSTSIZE != 256))
#error struct utmp member char[] size(s) have changed!
#endif

#if EMPTY != 0 || RUN_LVL != 1 || BOOT_TIME != 2 || NEW_TIME != 3 || \
    OLD_TIME != 4
#error Values for the ut_type field of struct utmp changed
#endif

int last_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int last_main(int argc UNUSED_PARAM, char **argv UNUSED_PARAM)
{
    struct utmp ut;
    int n, file = STDIN_FILENO;
    time_t t_tmp;
    off_t pos;
    static const char _ut_usr[] ALIGN1 =
            "runlevel\0" "reboot\0" "shutdown\0";
    static const char _ut_lin[] ALIGN1 =
            "~\0" "{\0" "|\0" /* "LOGIN\0" "date\0" */;
    enum {
        TYPE_RUN_LVL = RUN_LVL,         /* 1 */
        TYPE_BOOT_TIME = BOOT_TIME,     /* 2 */
        TYPE_SHUTDOWN_TIME = SHUTDOWN_TIME
    };
    enum {
        _TILDE = EMPTY, /* 0 */
        TYPE_NEW_TIME,  /* NEW_TIME, 3 */
        TYPE_OLD_TIME   /* OLD_TIME, 4 */
    };

    if (argv[1]) {
        bb_show_usage();
    }
    file = xopen(bb_path_wtmp_file, O_RDONLY);

    printf("%-10s %-14s %-18s %-12.12s %s\n",
        "USER", "TTY", "HOST", "LOGIN", "TIME");
    /* yikes. We reverse over the file and that is a not too elegant way */
    pos = xlseek(file, 0, SEEK_END);
    pos = lseek(file, pos - sizeof(ut), SEEK_SET);
    while ((n = full_read(file, &ut, sizeof(ut))) > 0) {
        if (n != sizeof(ut)) {
            bb_perror_msg_and_die("short read");
        }
        n = index_in_strings(_ut_lin, ut.ut_line);
        if (n == _TILDE) { /* '~' */
#if 1
/* do we really need to be cautious here? */
            n = index_in_strings(_ut_usr, ut.ut_user);
            if (++n > 0)
                ut.ut_type = n != 3 ? n : SHUTDOWN_TIME;
#else
            if (strncmp(ut.ut_user, "shutdown", 8) == 0)
                ut.ut_type = SHUTDOWN_TIME;
            else if (strncmp(ut.ut_user, "reboot", 6) == 0)
                ut.ut_type = BOOT_TIME;
            else if (strncmp(ut.ut_user, "runlevel", 8) == 0)
                ut.ut_type = RUN_LVL;
#endif
        } else {
            if (ut.ut_user[0] == '\0' || strcmp(ut.ut_user, "LOGIN") == 0) {
                /* Don't bother.  This means we can't find how long
                 * someone was logged in for.  Oh well. */
                goto next;
            }
            if (ut.ut_type != DEAD_PROCESS
             && ut.ut_user[0]
             && ut.ut_line[0]
            ) {
                ut.ut_type = USER_PROCESS;
            }
            if (strcmp(ut.ut_user, "date") == 0) {
                if (n == TYPE_OLD_TIME) { /* '|' */
                    ut.ut_type = OLD_TIME;
                }
                if (n == TYPE_NEW_TIME) { /* '{' */
                    ut.ut_type = NEW_TIME;
                }
            }
        }

        if (ut.ut_type != USER_PROCESS) {
            switch (ut.ut_type) {
                case OLD_TIME:
                case NEW_TIME:
                case RUN_LVL:
                case SHUTDOWN_TIME:
                    goto next;
                case BOOT_TIME:
                    strcpy(ut.ut_line, "system boot");
            }
        }
        /* manpages say ut_tv.tv_sec *is* time_t,
         * but some systems have it wrong */
        t_tmp = (time_t)ut.ut_tv.tv_sec;
        printf("%-10s %-14s %-18s %-12.12s\n",
            ut.ut_user, ut.ut_line, ut.ut_host, ctime(&t_tmp) + 4);
 next:
        pos -= sizeof(ut);
        if (pos <= 0)
            break; /* done. */
        xlseek(file, pos, SEEK_SET);
    }

    fflush_stdout_and_exit(EXIT_SUCCESS);
}