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 "long-options.h"
  26 #include "quote.h"
  27 #include "readutmp.h"
  28
  29 /* The official name of this program (e.g., no 'g' prefix).  */
  30 #define PROGRAM_NAME "users"
  31
  32 #define AUTHORS \
  33   proper_name ("Joseph Arceneaux"), \
  34   proper_name ("David MacKenzie")
  35
  36 static int
  37 userid_compare (const void *v_a, const void *v_b)
  38 {
  39   char **a = (char **) v_a;
  40   char **b = (char **) v_b;
  41   return strcmp (*a, *b);
  42 }
  43
  44 static void
  45 list_entries_users (idx_t n, struct gl_utmp const *this)
  46 {
  47   char **u = xinmalloc (n, sizeof *u);
  48   idx_t i;
  49   idx_t n_entries = 0;
  50
  51   while (n--)
  52     {
  53       if (IS_USER_PROCESS (this))
  54         {
  55           char *trimmed_name;
  56
  57           trimmed_name = extract_trimmed_name (this);
  58
  59           u[n_entries] = trimmed_name;
  60           ++n_entries;
  61         }
  62       this++;
  63     }
  64
  65   qsort (u, n_entries, sizeof (u[0]), userid_compare);
  66
  67   for (i = 0; i < n_entries; i++)
  68     {
  69       char c = (i < n_entries - 1 ? ' ' : '\n');
  70       fputs (u[i], stdout);
  71       putchar (c);
  72     }
  73
  74   for (i = 0; i < n_entries; i++)
  75     free (u[i]);
  76   free (u);
  77 }
  78
  79 /* Display a list of users on the system, according to utmp file FILENAME.
  80    Use read_utmp OPTIONS to read FILENAME.  */
  81
  82 static void
  83 users (char const *filename, int options)
  84 {
  85   idx_t n_users;
  86   struct gl_utmp *utmp_buf;
  87   options |= READ_UTMP_USER_PROCESS;
  88   if (read_utmp (filename, &n_users, &utmp_buf, options) != 0)
  89     error (EXIT_FAILURE, errno, "%s", quotef (filename));
  90
  91   list_entries_users (n_users, utmp_buf);
  92
  93   free (utmp_buf);
  94 }
  95
  96 void
  97 usage (int status)
  98 {
  99   if (status != EXIT_SUCCESS)
 100     emit_try_help ();
 101   else
 102     {
 103       printf (_("Usage: %s [OPTION]... [FILE]\n"), program_name);
 104       printf (_("\
 105 Output who is currently logged in according to FILE.\n\
 106 If FILE is not specified, use %s.  %s as FILE is common.\n\
 107 \n\
 108 "),
 109               UTMP_FILE, WTMP_FILE);
 110       fputs (HELP_OPTION_DESCRIPTION, stdout);
 111       fputs (VERSION_OPTION_DESCRIPTION, stdout);
 112       emit_ancillary_info (PROGRAM_NAME);
 113     }
 114   exit (status);
 115 }
 116
 117 int
 118 main (int argc, char **argv)
 119 {
 120   initialize_main (&argc, &argv);
 121   set_program_name (argv[0]);
 122   setlocale (LC_ALL, "");
 123   bindtextdomain (PACKAGE, LOCALEDIR);
 124   textdomain (PACKAGE);
 125
 126   atexit (close_stdout);
 127
 128   parse_gnu_standard_options_only (argc, argv, PROGRAM_NAME, PACKAGE_NAME,
 129                                    Version, true, usage, AUTHORS,
 130                                    (char const *) nullptr);
 131
 132   switch (argc - optind)
 133     {
 134     case 0:                     /* users */
 135       users (UTMP_FILE, READ_UTMP_CHECK_PIDS);
 136       break;
 137
 138     case 1:                     /* users <utmp file> */
 139       users (argv[optind], 0);
 140       break;
 141
 142     default:                    /* lose */
 143       error (0, 0, _("extra operand %s"), quote (argv[optind + 1]));
 144       usage (EXIT_FAILURE);
 145     }
 146
 147   return EXIT_SUCCESS;
 148 }