Recreate repo

user.c

@@ -0,0 +1,49 @@
+/* SPDX-License-Identifier: GPL-3.0-only */
+/* SPDX-FileCopyrightText: 2026 afiw <afiw@linuxposting.xyz> */
+
+/*
+ * can - query filesystem permissions
+ * Copyright (C) 2026 afiw <afiw@linuxposting.xyz>
+ *
+ * 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, exclusively version 3 of the License.
+ *
+ * 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/>.
+ */
+
+#include <err.h>
+#include <grp.h>
+#include <pwd.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include "action.h"
+#include "user.h"
+
+bool can_user(struct passwd* pw, enum action action, char const* path) {
+  gid_t groups_a[1];            /* just to be sure, passing stack memory or nullptr might invoke UB */
+  gid_t* groups = groups_a;
+  int ngroups = 0;
+  struct stat st;
+  if (stat(path, &st) == -1) {
+    err(EXIT_FAILURE, "%s", path); }
+  if (st.st_mode & other_bit_of_action(action)) {
+    return true; }
+  if (pw->pw_uid == st.st_uid) {
+    if (st.st_mode & user_bit_of_action(action)) {
+      return true; } }
+  (void)getgrouplist(pw->pw_name, pw->pw_gid, groups, &ngroups); /* just to get the value of ngroups */
+  groups = malloc(ngroups * sizeof(*groups));
+  (void)getgrouplist(pw->pw_name, pw->pw_gid, groups, &ngroups); /* getgrouplist doesn't fail */  
+  for (int i = 0; i < ngroups; ++i) {
+    if (groups[i] == st.st_gid) {
+      if (st.st_mode & group_bit_of_action(action)) {
+        return true; } } }
+  return false; }