src/whoami.c

   1 /* whoami -- print effective userid
   2
   3    Copyright (C) 1989-2022 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 "die.h"
  28 #include "error.h"
  29 #include "long-options.h"
  30 #include "quote.h"
  31
  32 /* The official name of this program (e.g., no 'g' prefix).  */
  33 #define PROGRAM_NAME "whoami"
  34
  35 #define AUTHORS proper_name ("Richard Mlynarik")
  36
  37 void
  38 usage (int status)
  39 {
  40   if (status != EXIT_SUCCESS)
  41     emit_try_help ();
  42   else
  43     {
  44       printf (_("Usage: %s [OPTION]...\n"), program_name);
  45       fputs (_("\
  46 Print the user name associated with the current effective user ID.\n\
  47 Same as id -un.\n\
  48 \n\
  49 "), stdout);
  50       fputs (HELP_OPTION_DESCRIPTION, stdout);
  51       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  52       emit_ancillary_info (PROGRAM_NAME);
  53     }
  54   exit (status);
  55 }
  56
  57 int
  58 main (int argc, char **argv)
  59 {
  60   struct passwd *pw;
  61   uid_t uid;
  62   uid_t NO_UID = -1;
  63
  64   initialize_main (&argc, &argv);
  65   set_program_name (argv[0]);
  66   setlocale (LC_ALL, "");
  67   bindtextdomain (PACKAGE, LOCALEDIR);
  68   textdomain (PACKAGE);
  69
  70   atexit (close_stdout);
  71
  72   parse_gnu_standard_options_only (argc, argv, PROGRAM_NAME, PACKAGE_NAME,
  73                                    Version, true, usage, AUTHORS,
  74                                    (char const *) NULL);
  75
  76   if (optind != argc)
  77     {
  78       error (0, 0, _("extra operand %s"), quote (argv[optind]));
  79       usage (EXIT_FAILURE);
  80     }
  81
  82   errno = 0;
  83   uid = geteuid ();
  84   pw = (uid == NO_UID && errno ? NULL : getpwuid (uid));
  85   if (!pw)
  86     die (EXIT_FAILURE, errno, _("cannot find name for user ID %lu"),
  87          (unsigned long int) uid);
  88   puts (pw->pw_name);
  89   return EXIT_SUCCESS;
  90 }