src/whoami.c

   1 /* whoami -- print effective userid
   2
   3    Copyright (C) 1989-2024 Free Software Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation, either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 /* Equivalent to 'id -un'. */
  19 /* Written by Richard Mlynarik. */
  20
  21 #include <config.h>
  22 #include <stdio.h>
  23 #include <sys/types.h>
  24 #include <pwd.h>
  25
  26 #include "system.h"
  27 #include "long-options.h"
  28 #include "quote.h"
  29
  30 /* The official name of this program (e.g., no 'g' prefix).  */
  31 #define PROGRAM_NAME "whoami"
  32
  33 #define AUTHORS proper_name ("Richard Mlynarik")
  34
  35 void
  36 usage (int status)
  37 {
  38   if (status != EXIT_SUCCESS)
  39     emit_try_help ();
  40   else
  41     {
  42       printf (_("Usage: %s [OPTION]...\n"), program_name);
  43       fputs (_("\
  44 Print the user name associated with the current effective user ID.\n\
  45 Same as id -un.\n\
  46 \n\
  47 "), stdout);
  48       fputs (HELP_OPTION_DESCRIPTION, stdout);
  49       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  50       emit_ancillary_info (PROGRAM_NAME);
  51     }
  52   exit (status);
  53 }
  54
  55 int
  56 main (int argc, char **argv)
  57 {
  58   struct passwd *pw;
  59   uid_t uid;
  60   uid_t NO_UID = -1;
  61
  62   initialize_main (&argc, &argv);
  63   set_program_name (argv[0]);
  64   setlocale (LC_ALL, "");
  65   bindtextdomain (PACKAGE, LOCALEDIR);
  66   textdomain (PACKAGE);
  67
  68   atexit (close_stdout);
  69
  70   parse_gnu_standard_options_only (argc, argv, PROGRAM_NAME, PACKAGE_NAME,
  71                                    Version, true, usage, AUTHORS,
  72                                    (char const *) nullptr);
  73
  74   if (optind != argc)
  75     {
  76       error (0, 0, _("extra operand %s"), quote (argv[optind]));
  77       usage (EXIT_FAILURE);
  78     }
  79
  80   errno = 0;
  81   uid = geteuid ();
  82   pw = uid == NO_UID && errno ? nullptr : getpwuid (uid);
  83   if (!pw)
  84     error (EXIT_FAILURE, errno, _("cannot find name for user ID %lu"),
  85            (unsigned long int) uid);
  86   puts (pw->pw_name);
  87   return EXIT_SUCCESS;
  88 }