diff --git a/src/helper/docs/cmd_parse.rs b/src/helper/docs/cmd_parse.rs
index e96c546..0b31383 100644
--- a/src/helper/docs/cmd_parse.rs
+++ b/src/helper/docs/cmd_parse.rs
@@ -6,12 +6,19 @@ use std::collections::HashMap;
 /// `<cmd> [<subcommand>] [<args>]`
 /// the subcommand and args are optional.
 ///
+/// This function will add at least the `cmd` key to the `values_map` and 3 keys at most.
+/// - `cmd`: The command name.
+/// - `subcommand`: The command subcommand.
+/// - `args`: The command arguments.
+///
 /// # Example
 /// ```
 /// # use halp::helper::docs::cmd_parse::parse_cmd;
+/// # use std::collections::HashMap;
 ///
 /// let git_commit = "git commit -a";
-/// let mut values_map = parse_cmd(git_commit);
+/// let mut values_map = HashMap::with_capacity(3);
+/// parse_cmd(git_commit, &mut values_map);
 /// assert!(values_map.contains_key("cmd"));
 /// assert_eq!(values_map.get("cmd").unwrap(), "git");
 /// assert!(values_map.contains_key("subcommand"));
@@ -22,8 +29,7 @@ use std::collections::HashMap;
 ///
 /// # Panics
 /// THIS FUNCTION WILL PANIC IF THE COMMAND STRING IS EMPTY.
-pub fn parse_cmd(cmd: &str) -> HashMap<String, String> {
-    let mut values_map = HashMap::with_capacity(3);
+pub fn parse_cmd(cmd: &str, values_map: &mut HashMap<String, String>) {
     let cmd = cmd.trim().to_string();
     let mut iter = cmd.split_whitespace();
     // The `cmd` should be the first value.
@@ -40,7 +46,6 @@ pub fn parse_cmd(cmd: &str) -> HashMap<String, String> {
             args.push_str(&format!(" {}", part));
         }
     }
-    values_map
 }
 
 #[cfg(test)]
@@ -51,7 +56,8 @@ mod tests {
     #[test]
     fn test_parse_complete_cmd() {
         let git_commit = "git commit -a";
-        let values_map = parse_cmd(git_commit);
+        let mut  values_map = HashMap::with_capacity(3);
+        parse_cmd(git_commit, &mut values_map);
         assert!(values_map.contains_key("cmd"));
         assert_eq!(values_map.get("cmd"), Some(&"git".to_string()));
         assert!(values_map.contains_key("subcommand"));
@@ -63,7 +69,8 @@ mod tests {
     #[test]
     fn test_parse_cmd_with_no_args() {
         let git_commit = "git commit";
-        let values_map = parse_cmd(git_commit);
+        let mut values_map = HashMap::with_capacity(3);
+        parse_cmd(git_commit, &mut values_map);
         assert!(values_map.contains_key("cmd"));
         assert_eq!(values_map.get("cmd"), Some(&"git".to_string()));
         assert!(values_map.contains_key("subcommand"));
@@ -74,7 +81,8 @@ mod tests {
     #[test]
     fn test_parse_cmd_with_no_subcommand() {
         let git_commit = "git";
-        let values_map = parse_cmd(git_commit);
+        let mut values_map = HashMap::with_capacity(3);
+        parse_cmd(git_commit, &mut values_map);
         assert!(values_map.contains_key("cmd"));
         assert_eq!(values_map.get("cmd"), Some(&"git".to_string()));
         assert!(!values_map.contains_key("subcommand"));
@@ -84,7 +92,8 @@ mod tests {
     #[test]
     fn test_parse_cmd_with_no_subcommand_and_args() {
         let git_commit = "git";
-        let values_map = parse_cmd(git_commit);
+        let mut values_map = HashMap::with_capacity(3);
+        parse_cmd(git_commit, &mut values_map);
         assert!(values_map.contains_key("cmd"));
         assert_eq!(values_map.get("cmd"), Some(&"git".to_string()));
         assert!(!values_map.contains_key("subcommand"));
@@ -94,7 +103,8 @@ mod tests {
     #[test]
     fn test_parse_cmd_with_args_and_no_subcommand() {
         let command = "ps -aux";
-        let values_map = parse_cmd(command);
+        let mut values_map = HashMap::with_capacity(3);
+        parse_cmd(command, &mut values_map);
         assert!(values_map.contains_key("cmd"));
         assert_eq!(values_map.get("cmd"), Some(&"ps".to_string()));
         assert!(!values_map.contains_key("subcommand"));
@@ -105,7 +115,8 @@ mod tests {
     #[test]
     fn test_parse_cmd_with_two_args_and_no_subcommand() {
         let command = "ps -aux -l";
-        let values_map = parse_cmd(command);
+        let mut values_map = HashMap::with_capacity(3);
+        parse_cmd(command, &mut values_map);
         assert!(values_map.contains_key("cmd"));
         assert_eq!(values_map.get("cmd"), Some(&"ps".to_string()));
         assert!(!values_map.contains_key("subcommand"));
@@ -116,7 +127,8 @@ mod tests {
     #[test]
     fn test_parse_cmd_with_three_args_and_subcommand() {
         let command = "git commit -a -m \"commit message\"";
-        let values_map = parse_cmd(command);
+        let mut values_map = HashMap::with_capacity(3);
+        parse_cmd(command, &mut values_map);
         assert!(values_map.contains_key("cmd"));
         assert_eq!(values_map.get("cmd"), Some(&"git".to_string()));
         assert!(values_map.contains_key("subcommand"));