Merged with chkgrp and renamed to chkusr.

chkgrp-native-min.c

@@ -0,0 +1,60 @@
+/**
+ * chkgrp-min-native is a program that checks if a user is a member of a group.
+ *
+ * Author: Johannes Findeisen <you@hanez.org> - 2025
+ * Homepage: https://git.xw3.org/hanez/chkgrp
+ * License: Apache-2.0 (see LICENSE)
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define MAX_LINE 1024
+#define MAX_NAME 256
+
+int main(int argc, char *argv[])
+{
+    if (argc != 3)
+        return 2;
+
+    const char *username = argv[1];
+    const char *groupname = argv[2];
+
+    if (strlen(username) > MAX_NAME || strlen(groupname) > MAX_NAME)
+        return 2;
+
+    FILE *fp = fopen("/etc/group", "r");
+    if (!fp)
+        return 2;
+
+    char line[MAX_LINE];
+    while (fgets(line, sizeof(line), fp)) {
+        char *grp = strtok(line, ":");
+        if (!grp || strcmp(grp, groupname) != 0)
+            continue;
+
+        strtok(NULL, ":"); // skip password
+        strtok(NULL, ":"); // skip GID
+
+        char *members = strtok(NULL, ":\n");
+        if (!members) break;
+
+        char *m = strtok(members, ",");
+        while (m) {
+            if (!strcmp(m, username)) {
+                puts("Yes");
+                fclose(fp);
+                return 0;
+            }
+            m = strtok(NULL, ",");
+        }
+
+        break; // group matched, no user found
+    }
+
+    fclose(fp);
+    puts("No");
+    return 1;
+}
+