From fe27808a6562c1d7eb9a041c81a10e090acfc3ea Mon Sep 17 00:00:00 2001
From: Ting-Jun Wang <levi900227@gmail.com>
Date: Sat, 25 May 2024 18:35:26 +0800
Subject: [PATCH] docs: add comment

---
 tool/setup_uid.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/tool/setup_uid.c b/tool/setup_uid.c
index d9f32e9..7500b8d 100644
--- a/tool/setup_uid.c
+++ b/tool/setup_uid.c
@@ -38,6 +38,18 @@ bool check_user(char *filename, char *username, unsigned long *new_start) {
 }
 
 void insert_user(char *filename, char *username, unsigned long start) {
+    /*
+     * Insert the user into uid file
+     * It will setup the next start uid automatically
+     * == it will change /etc/subuid or /etc/subgid ==
+     *
+     * Args:
+     *      filename (char *): means the uid file (subuid or subgid).
+     *      username (char *): the user who run this excutable file.
+     *      new_start (unsigned long ): it's a value, means the next start uid
+     * Return:
+     *      No
+     */
     FILE *fp = fopen(filename, "a");
     
     if (fp == NULL) {