Userland: Add groups program

Userland/Utilities/groups.cpp

@@ -0,0 +1,82 @@
+/*
+ * Copyright (c) 2021, the SerenityOS developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Vector.h>
+#include <LibCore/Account.h>
+#include <LibCore/ArgsParser.h>
+#include <grp.h>
+#include <unistd.h>
+
+static void print_account_gids(const Core::Account& account)
+{
+ auto* gr = getgrgid(account.gid());
+ if (!gr) {
+ outln();
+ return;
+ }
+
+ out("{}", gr->gr_name);
+ for (auto& gid : account.extra_gids()) {
+ gr = getgrgid(gid);
+ out(" {}", gr->gr_name);
+ }
+ outln();
+}
+
+int main(int argc, char** argv)
+{
+ if (unveil("/etc/passwd", "r") < 0) {
+ perror("unveil");
+ return 1;
+ }
+
+ if (unveil("/etc/shadow", "r") < 0) {
+ perror("unveil");
+ return 1;
+ }
+
+ if (unveil("/etc/group", "r") < 0) {
+ perror("unveil");
+ return 1;
+ }
+
+ if (unveil(nullptr, nullptr) < 0) {
+ perror("unveil");
+ return 1;
+ }
+
+ if (pledge("stdio rpath", nullptr) < 0) {
+ perror("pledge");
+ return 1;
+ }
+
+ Vector<const char*> usernames;
+
+ Core::ArgsParser args_parser;
+ args_parser.set_general_help("Print group memberships for each username or, if no username is specified, for the current process.");
+ args_parser.add_positional_argument(usernames, "Usernames to list group memberships for", "usernames", Core::ArgsParser::Required::No);
+ args_parser.parse(argc, argv);
+
+ if (usernames.is_empty()) {
+ auto result = Core::Account::from_uid(geteuid());
+ if (result.is_error()) {
+ warnln("{}", result.error());
+ return 1;
+ }
+ print_account_gids(result.value());
+ }
+
+ for (auto username : usernames) {
+ auto result = Core::Account::from_name(username);
+ if (result.is_error()) {
+ warnln("{} '{}'", result.error(), username);
+ continue;
+ }
+ out("{} : ", username);
+ print_account_gids(result.value());
+ }
+ return 0;
+}