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+/* whoami -- print effective userid
+
+ Copyright (C) 1989-2022 Free Software Foundation, Inc.
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <https://www.gnu.org/licenses/>. */
+
+/* Equivalent to 'id -un'. */
+/* Written by Richard Mlynarik. */
+
+#include <config.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <pwd.h>
+
+#include "system.h"
+#include "die.h"
+#include "error.h"
+#include "long-options.h"
+#include "quote.h"
+
+/* The official name of this program (e.g., no 'g' prefix). */
+#define PROGRAM_NAME "whoami"
+
+#define AUTHORS proper_name ("Richard Mlynarik")
+
+void
+usage (int status)
+{
+ if (status != EXIT_SUCCESS)
+ emit_try_help ();
+ else
+ {
+ printf (_("Usage: %s [OPTION]...\n"), program_name);
+ fputs (_("\
+Print the user name associated with the current effective user ID.\n\
+Same as id -un.\n\
+\n\
+"), stdout);
+ fputs (HELP_OPTION_DESCRIPTION, stdout);
+ fputs (VERSION_OPTION_DESCRIPTION, stdout);
+ emit_ancillary_info (PROGRAM_NAME);
+ }
+ exit (status);
+}
+
+int
+main (int argc, char **argv)
+{
+ struct passwd *pw;
+ uid_t uid;
+ uid_t NO_UID = -1;
+
+ initialize_main (&argc, &argv);
+ set_program_name (argv[0]);
+ setlocale (LC_ALL, "");
+ bindtextdomain (PACKAGE, LOCALEDIR);
+ textdomain (PACKAGE);
+
+ atexit (close_stdout);
+
+ parse_gnu_standard_options_only (argc, argv, PROGRAM_NAME, PACKAGE_NAME,
+ Version, true, usage, AUTHORS,
+ (char const *) NULL);
+
+ if (optind != argc)
+ {
+ error (0, 0, _("extra operand %s"), quote (argv[optind]));
+ usage (EXIT_FAILURE);
+ }
+
+ errno = 0;
+ uid = geteuid ();
+ pw = (uid == NO_UID && errno ? NULL : getpwuid (uid));
+ if (!pw)
+ die (EXIT_FAILURE, errno, _("cannot find name for user ID %lu"),
+ (unsigned long int) uid);
+ puts (pw->pw_name);
+ return EXIT_SUCCESS;
+}