src/whoami.c

   1 /* whoami -- print effective userid
   2
   3    Copyright (C) 1989-2017 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 <http://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 #include <getopt.h>
  26
  27 #include "system.h"
  28 #include "die.h"
  29 #include "error.h"
  30 #include "long-options.h"
  31 #include "quote.h"
  32
  33 /* The official name of this program (e.g., no 'g' prefix).  */
  34 #define PROGRAM_NAME "whoami"
  35
  36 #define AUTHORS proper_name ("Richard Mlynarik")
  37
  38 void
  39 usage (int status)
  40 {
  41   if (status != EXIT_SUCCESS)
  42     emit_try_help ();
  43   else
  44     {
  45       printf (_("Usage: %s [OPTION]...\n"), program_name);
  46       fputs (_("\
  47 Print the user name associated with the current effective user ID.\n\
  48 Same as id -un.\n\
  49 \n\
  50 "), stdout);
  51       fputs (HELP_OPTION_DESCRIPTION, stdout);
  52       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  53       emit_ancillary_info (PROGRAM_NAME);
  54     }
  55   exit (status);
  56 }
  57
  58 int
  59 main (int argc, char **argv)
  60 {
  61   struct passwd *pw;
  62   uid_t uid;
  63   uid_t NO_UID = -1;
  64
  65   initialize_main (&argc, &argv);
  66   set_program_name (argv[0]);
  67   setlocale (LC_ALL, "");
  68   bindtextdomain (PACKAGE, LOCALEDIR);
  69   textdomain (PACKAGE);
  70
  71   atexit (close_stdout);
  72
  73   parse_long_options (argc, argv, PROGRAM_NAME, PACKAGE_NAME, Version,
  74                       usage, AUTHORS, (char const *) NULL);
  75   if (getopt_long (argc, argv, "", NULL, NULL) != -1)
  76     usage (EXIT_FAILURE);
  77
  78   if (optind != argc)
  79     {
  80       error (0, 0, _("extra operand %s"), quote (argv[optind]));
  81       usage (EXIT_FAILURE);
  82     }
  83
  84   errno = 0;
  85   uid = geteuid ();
  86   pw = (uid == NO_UID && errno ? NULL : getpwuid (uid));
  87   if (!pw)
  88     die (EXIT_FAILURE, errno, _("cannot find name for user ID %lu"),
  89          (unsigned long int) uid);
  90   puts (pw->pw_name);
  91   return EXIT_SUCCESS;
  92 }