diff --git a/src/cmdargs.rs b/src/cmdargs.rs
new file mode 100644
index 0000000..25b77db
--- /dev/null
+++ b/src/cmdargs.rs
@@ -0,0 +1,65 @@
+use std::path::PathBuf;
+use std::process::exit;
+
+use clap::Parser;
+use num_cpus;
+
+use crate::output as op;
+
+#[derive(Parser)]
+#[command(name = "fcnt")]
+#[command(version = "0.2.1")]
+#[command(about = "Count the total number of files in given directories.")]
+pub struct CmdArgParser {
+    /// the directories (default: ./)
+    pub directories: Vec<String>,
+
+    /// count all regular and hidden files.
+    #[arg(short = 'a')]
+    pub all_files: bool,
+
+    /// count the total size of files.
+    #[arg(short = 's')]
+    pub with_size: bool,
+
+    /// non-recursive mode (files in sub-directories will be ignored).
+    #[arg(short = 'R')]
+    pub non_recursive: bool,
+
+    /// the number of threads for traversal (invalid in `non_recursive` mode).
+    #[arg(short = 't')]
+    pub n_thread: Option<usize>,
+}
+
+impl CmdArgParser {
+    pub fn get_threads_num(&self) -> usize {
+        match self.n_thread {
+            Some(num) => return num,
+            None => {
+                let n_cpu = num_cpus::get();
+                return if n_cpu >= 4 { n_cpu } else { 4 };
+            }
+        }
+    }
+
+    pub fn get_directories(&self) -> Vec<PathBuf> {
+        let mut directories: Vec<PathBuf> = vec![];
+        if self.directories.is_empty() {
+            directories.push(PathBuf::from("./"));
+        } else {
+            for dir in self.directories.iter().map(|p| PathBuf::from(p)) {
+                if dir.is_dir() {
+                    directories.push(dir);
+                } else {
+                    let msg = format!("{:?} is not a directory.", dir);
+                    println!("{}", op::warn(&msg));
+                }
+            }
+            if directories.is_empty() {
+                println!("{}", op::err(&"fcnt: no directory found."));
+                exit(1);
+            }
+        }
+        return directories;
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index e139c74..ecef579 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,17 +1,14 @@
+mod cmdargs;
 mod output;
 mod walker;
 
-use std::path::PathBuf;
-use std::process::exit;
-
 use clap::Parser;
-use num_cpus::get as cpu_count;
-
+use cmdargs::CmdArgParser;
 use walker::Counter;
 
 fn main() {
     // parse cmd-line args and get directories
-    let args = CmdLineArgs::parse();
+    let args = CmdArgParser::parse();
 
     // walk all files
     let directories = args.get_directories();
@@ -35,61 +32,3 @@ fn main() {
 
     Counter::output(&counters, args.with_size);
 }
-
-#[derive(Parser)]
-#[command(name = "fcnt")]
-#[command(version = "0.2.1")]
-#[command(about = "Count the total number of files in given directories.")]
-struct CmdLineArgs {
-    /// the directories (default: ./)
-    directories: Vec<String>,
-
-    /// count all regular and hidden files.
-    #[arg(short = 'a')]
-    all_files: bool,
-
-    /// count the total size of files.
-    #[arg(short = 's')]
-    with_size: bool,
-
-    /// non-recursive mode (files in sub-directories will be ignored).
-    #[arg(short = 'R')]
-    non_recursive: bool,
-
-    /// the number of threads for traversal (invalid in `non_recursive` mode).
-    #[arg(short = 't')]
-    n_thread: Option<usize>,
-}
-
-impl CmdLineArgs {
-    pub fn get_threads_num(&self) -> usize {
-        match self.n_thread {
-            Some(num) => num,
-            None => {
-                let n_cpu = cpu_count();
-                return if n_cpu >= 4 { n_cpu } else { 4 };
-            }
-        }
-    }
-
-    pub fn get_directories(&self) -> Vec<PathBuf> {
-        let mut directories: Vec<PathBuf> = vec![];
-        if self.directories.is_empty() {
-            directories.push(PathBuf::from("./"));
-        } else {
-            for dir in self.directories.iter().map(|p| PathBuf::from(p)) {
-                if dir.is_dir() {
-                    directories.push(dir);
-                } else {
-                    let msg = format!("{:?} is not a directory.", dir);
-                    println!("{}", output::warn(&msg));
-                }
-            }
-            if directories.is_empty() {
-                println!("{}", output::err(&"fcnt: no directory found."));
-                exit(1);
-            }
-        }
-        return directories;
-    }
-}