src/whoami.c

   1 /* whoami -- print effective userid
   2
   3    Copyright (C) 1989-1997, 1999-2002, 2004-2005, 2007-2012 Free Software
   4    Foundation, Inc.
   5
   6    This program is free software: you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation, either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  18
  19 /* Equivalent to `id -un'. */
  20 /* Written by Richard Mlynarik. */
  21
  22 #include <config.h>
  23 #include <stdio.h>
  24 #include <sys/types.h>
  25 #include <pwd.h>
  26 #include <getopt.h>
  27
  28 #include "system.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 ();
  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     {
  89       puts (pw->pw_name);
  90       exit (EXIT_SUCCESS);
  91     }
  92   fprintf (stderr, _("%s: cannot find name for user ID %lu\n"),
  93            program_name, (unsigned long int) uid);
  94   exit (EXIT_FAILURE);
  95 }