src/users.c

   1 /* GNU's users.
   2    Copyright (C) 1992-2023 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation, either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 /* Written by jla; revised by djm */
  18
  19 #include <config.h>
  20 #include <stdio.h>
  21
  22 #include <sys/types.h>
  23 #include "system.h"
  24
  25 #include "die.h"
  26 #include "error.h"
  27 #include "long-options.h"
  28 #include "quote.h"
  29 #include "readutmp.h"
  30
  31 /* The official name of this program (e.g., no 'g' prefix).  */
  32 #define PROGRAM_NAME "users"
  33
  34 #define AUTHORS \
  35   proper_name ("Joseph Arceneaux"), \
  36   proper_name ("David MacKenzie")
  37
  38 static int
  39 userid_compare (const void *v_a, const void *v_b)
  40 {
  41   char **a = (char **) v_a;
  42   char **b = (char **) v_b;
  43   return strcmp (*a, *b);
  44 }
  45
  46 static void
  47 list_entries_users (size_t n, const STRUCT_UTMP *this)
  48 {
  49   char **u = xnmalloc (n, sizeof *u);
  50   size_t i;
  51   size_t n_entries = 0;
  52
  53   while (n--)
  54     {
  55       if (IS_USER_PROCESS (this))
  56         {
  57           char *trimmed_name;
  58
  59           trimmed_name = extract_trimmed_name (this);
  60
  61           u[n_entries] = trimmed_name;
  62           ++n_entries;
  63         }
  64       this++;
  65     }
  66
  67   qsort (u, n_entries, sizeof (u[0]), userid_compare);
  68
  69   for (i = 0; i < n_entries; i++)
  70     {
  71       char c = (i < n_entries - 1 ? ' ' : '\n');
  72       fputs (u[i], stdout);
  73       putchar (c);
  74     }
  75
  76   for (i = 0; i < n_entries; i++)
  77     free (u[i]);
  78   free (u);
  79 }
  80
  81 /* Display a list of users on the system, according to utmp file FILENAME.
  82    Use read_utmp OPTIONS to read FILENAME.  */
  83
  84 static void
  85 users (char const *filename, int options)
  86 {
  87   size_t n_users;
  88   STRUCT_UTMP *utmp_buf;
  89
  90   if (read_utmp (filename, &n_users, &utmp_buf, options) != 0)
  91     die (EXIT_FAILURE, errno, "%s", quotef (filename));
  92
  93   list_entries_users (n_users, utmp_buf);
  94
  95   free (utmp_buf);
  96 }
  97
  98 void
  99 usage (int status)
 100 {
 101   if (status != EXIT_SUCCESS)
 102     emit_try_help ();
 103   else
 104     {
 105       printf (_("Usage: %s [OPTION]... [FILE]\n"), program_name);
 106       printf (_("\
 107 Output who is currently logged in according to FILE.\n\
 108 If FILE is not specified, use %s.  %s as FILE is common.\n\
 109 \n\
 110 "),
 111               UTMP_FILE, WTMP_FILE);
 112       fputs (HELP_OPTION_DESCRIPTION, stdout);
 113       fputs (VERSION_OPTION_DESCRIPTION, stdout);
 114       emit_ancillary_info (PROGRAM_NAME);
 115     }
 116   exit (status);
 117 }
 118
 119 int
 120 main (int argc, char **argv)
 121 {
 122   initialize_main (&argc, &argv);
 123   set_program_name (argv[0]);
 124   setlocale (LC_ALL, "");
 125   bindtextdomain (PACKAGE, LOCALEDIR);
 126   textdomain (PACKAGE);
 127
 128   atexit (close_stdout);
 129
 130   parse_gnu_standard_options_only (argc, argv, PROGRAM_NAME, PACKAGE_NAME,
 131                                    Version, true, usage, AUTHORS,
 132                                    (char const *) NULL);
 133
 134   switch (argc - optind)
 135     {
 136     case 0:                     /* users */
 137       users (UTMP_FILE, READ_UTMP_CHECK_PIDS);
 138       break;
 139
 140     case 1:                     /* users <utmp file> */
 141       users (argv[optind], 0);
 142       break;
 143
 144     default:                    /* lose */
 145       error (0, 0, _("extra operand %s"), quote (argv[optind + 1]));
 146       usage (EXIT_FAILURE);
 147     }
 148
 149   return EXIT_SUCCESS;
 150 }