release/src/router/busybox/miscutils/last.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * last implementation for busybox
   4  *
   5  * Copyright (C) 2003-2004 by Erik Andersen <andersen@codepoet.org>
   6  *
   7  * Licensed under the GPL version 2, see the file LICENSE in this tarball.
   8  */
   9
  10 #include "libbb.h"
  11 #include <utmp.h>
  12
  13 /* NB: ut_name and ut_user are the same field, use only one name (ut_user)
  14  * to reduce confusion */
  15
  16 #ifndef SHUTDOWN_TIME
  17 #  define SHUTDOWN_TIME 254
  18 #endif
  19
  20 /* Grr... utmp char[] members do not have to be nul-terminated.
  21  * Do what we can while still keeping this reasonably small.
  22  * Note: We are assuming the ut_id[] size is fixed at 4. */
  23
  24 #if defined UT_LINESIZE \
  25         && ((UT_LINESIZE != 32) || (UT_NAMESIZE != 32) || (UT_HOSTSIZE != 256))
  26 #error struct utmp member char[] size(s) have changed!
  27 #elif defined __UT_LINESIZE \
  28         && ((__UT_LINESIZE != 32) || (__UT_NAMESIZE != 64) || (__UT_HOSTSIZE != 256))
  29 #error struct utmp member char[] size(s) have changed!
  30 #endif
  31
  32 #if EMPTY != 0 || RUN_LVL != 1 || BOOT_TIME != 2 || NEW_TIME != 3 || \
  33         OLD_TIME != 4
  34 #error Values for the ut_type field of struct utmp changed
  35 #endif
  36
  37 int last_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  38 int last_main(int argc, char **argv UNUSED_PARAM)
  39 {
  40         struct utmp ut;
  41         int n, file = STDIN_FILENO;
  42         time_t t_tmp;
  43         off_t pos;
  44         static const char _ut_usr[] ALIGN1 =
  45                         "runlevel\0" "reboot\0" "shutdown\0";
  46         static const char _ut_lin[] ALIGN1 =
  47                         "~\0" "{\0" "|\0" /* "LOGIN\0" "date\0" */;
  48         enum {
  49                 TYPE_RUN_LVL = RUN_LVL,         /* 1 */
  50                 TYPE_BOOT_TIME = BOOT_TIME,     /* 2 */
  51                 TYPE_SHUTDOWN_TIME = SHUTDOWN_TIME
  52         };
  53         enum {
  54                 _TILDE = EMPTY,                         /* 0 */
  55                 TYPE_NEW_TIME,  /* NEW_TIME, 3 */
  56                 TYPE_OLD_TIME   /* OLD_TIME, 4 */
  57         };
  58
  59         if (argc > 1) {
  60                 bb_show_usage();
  61         }
  62         file = xopen(bb_path_wtmp_file, O_RDONLY);
  63
  64         printf("%-10s %-14s %-18s %-12.12s %s\n",
  65                "USER", "TTY", "HOST", "LOGIN", "TIME");
  66         /* yikes. We reverse over the file and that is a not too elegant way */
  67         pos = xlseek(file, 0, SEEK_END);
  68         pos = lseek(file, pos - sizeof(ut), SEEK_SET);
  69         while ((n = full_read(file, &ut, sizeof(ut))) > 0) {
  70                 if (n != sizeof(ut)) {
  71                         bb_perror_msg_and_die("short read");
  72                 }
  73                 n = index_in_strings(_ut_lin, ut.ut_line);
  74                 if (n == _TILDE) { /* '~' */
  75 #if 1
  76 /* do we really need to be cautious here? */
  77                         n = index_in_strings(_ut_usr, ut.ut_user);
  78                         if (++n > 0)
  79                                 ut.ut_type = n != 3 ? n : SHUTDOWN_TIME;
  80 #else
  81                         if (strncmp(ut.ut_user, "shutdown", 8) == 0)
  82                                 ut.ut_type = SHUTDOWN_TIME;
  83                         else if (strncmp(ut.ut_user, "reboot", 6) == 0)
  84                                 ut.ut_type = BOOT_TIME;
  85                         else if (strncmp(ut.ut_user, "runlevel", 8) == 0)
  86                                 ut.ut_type = RUN_LVL;
  87 #endif
  88                 } else {
  89                         if (ut.ut_user[0] == '\0' || strcmp(ut.ut_user, "LOGIN") == 0) {
  90                                 /* Don't bother.  This means we can't find how long
  91                                  * someone was logged in for.  Oh well. */
  92                                 goto next;
  93                         }
  94                         if (ut.ut_type != DEAD_PROCESS
  95                          && ut.ut_user[0] && ut.ut_line[0]
  96                         ) {
  97                                 ut.ut_type = USER_PROCESS;
  98                         }
  99                         if (strcmp(ut.ut_user, "date") == 0) {
 100                                 if (n == TYPE_OLD_TIME) { /* '|' */
 101                                         ut.ut_type = OLD_TIME;
 102                                 }
 103                                 if (n == TYPE_NEW_TIME) { /* '{' */
 104                                         ut.ut_type = NEW_TIME;
 105                                 }
 106                         }
 107                 }
 108
 109                 if (ut.ut_type != USER_PROCESS) {
 110                         switch (ut.ut_type) {
 111                                 case OLD_TIME:
 112                                 case NEW_TIME:
 113                                 case RUN_LVL:
 114                                 case SHUTDOWN_TIME:
 115                                         goto next;
 116                                 case BOOT_TIME:
 117                                         strcpy(ut.ut_line, "system boot");
 118                         }
 119                 }
 120                 /* manpages say ut_tv.tv_sec *is* time_t,
 121                  * but some systems have it wrong */
 122                 t_tmp = (time_t)ut.ut_tv.tv_sec;
 123                 printf("%-10s %-14s %-18s %-12.12s\n",
 124                        ut.ut_user, ut.ut_line, ut.ut_host, ctime(&t_tmp) + 4);
 125  next:
 126                 pos -= sizeof(ut);
 127                 if (pos <= 0)
 128                         break; /* done. */
 129                 xlseek(file, pos, SEEK_SET);
 130         }
 131
 132         fflush_stdout_and_exit(EXIT_SUCCESS);
 133 }