diff --git a/README.md b/README.md
index 2560554..deda772 100644
--- a/README.md
+++ b/README.md
@@ -28,6 +28,9 @@ pulsarss --source https://path/to/feed.rss
 * `source`, `s` - RSS feed source (required)
 * `target`, `t` - Destination directory (`public` by default)
 * `update`, `u` - Update timeout in seconds (`60` by default)
+* `output`, `o` - Print output (`d` by default):
+  * `d` - debug
+  * `n` - disable
 
 ### Autostart
 
diff --git a/src/argument.rs b/src/argument.rs
index 8befa45..9c5877f 100644
--- a/src/argument.rs
+++ b/src/argument.rs
@@ -11,7 +11,11 @@ pub struct Argument {
     #[arg(short, long, default_value_t = String::from("public"))]
     pub target: String,
 
-    /// Update timeout in seconds (60 by default)
+    /// Update timeout in seconds (`60` by default)
     #[arg(short, long, default_value_t = 60)]
     pub update: u64,
+
+    /// Show output (`d` by default)
+    #[arg(short, long, default_value_t = String::from("d"))]
+    pub output: String,
 }
diff --git a/src/main.rs b/src/main.rs
index 85231d5..881e494 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,5 +1,7 @@
 mod argument;
+mod output;
 
+use output::Output;
 use std::error::Error;
 
 fn main() -> Result<(), Box<dyn Error>> {
@@ -8,16 +10,17 @@ fn main() -> Result<(), Box<dyn Error>> {
     use std::{thread::sleep, time::Duration};
 
     let argument = Argument::parse();
+    let output = Output::build(&argument.output);
 
-    let mut index: Vec<usize> = Vec::new();
+    output.debug("crawler started");
 
     loop {
-        crawl(&mut index, &argument.source, &argument.target)?;
+        crawl(&argument.source, &argument.target, &output)?;
         sleep(Duration::from_secs(argument.update));
     }
 }
 
-fn crawl(index: &mut Vec<usize>, source: &str, target: &str) -> Result<(), Box<dyn Error>> {
+fn crawl(source: &str, target: &str, output: &Output) -> Result<(), Box<dyn Error>> {
     use reqwest::blocking::get;
     use rss::Channel;
     use std::{
@@ -25,13 +28,18 @@ fn crawl(index: &mut Vec<usize>, source: &str, target: &str) -> Result<(), Box<d
         io::Write,
     };
 
-    for item in Channel::read_from(&get(source)?.bytes()?[..])?.items() {
-        let id = index.len() + 1;
+    output.debug("update begin");
 
-        let path = &path(id, target, item.pub_date().unwrap(), true)?;
+    let mut total = 0;
+    let mut exist = 0;
+    for item in Channel::read_from(&get(source)?.bytes()?[..])?.items() {
+        total += 1;
+
+        let path = &path(target, item.pub_date().unwrap(), true)?;
 
         if metadata(path).is_ok() {
-            continue; // skip existing records
+            exist += 1;
+            continue;
         }
 
         let mut file = File::create(path)?;
@@ -45,14 +53,17 @@ fn crawl(index: &mut Vec<usize>, source: &str, target: &str) -> Result<(), Box<d
             )
             .as_bytes(),
         )?;
-
-        index.push(id);
     }
 
+    output.debug(&format!(
+        "update completed (added: {} / exist: {exist} / total: {total})",
+        total - exist
+    ));
+
     Ok(())
 }
 
-fn path(_id: usize, base: &str, pub_date: &str, mkdir: bool) -> Result<String, Box<dyn Error>> {
+fn path(base: &str, pub_date: &str, mkdir: bool) -> Result<String, Box<dyn Error>> {
     use chrono::{DateTime, Datelike, Timelike};
     use std::{fs::create_dir_all, path::MAIN_SEPARATOR};
 
diff --git a/src/output.rs b/src/output.rs
new file mode 100644
index 0000000..fd18102
--- /dev/null
+++ b/src/output.rs
@@ -0,0 +1,29 @@
+use chrono::{DateTime, Utc};
+use std::time::SystemTime;
+
+struct Level {
+    debug: bool,
+}
+
+pub struct Output(Level);
+
+impl Output {
+    pub fn build(level: &str) -> Self {
+        Self(Level {
+            debug: level.contains("d"),
+            // @TODO other flags
+        })
+    }
+
+    pub fn debug(&self, message: &str) {
+        if self.0.debug {
+            eprintln!("[debug] [{}] {message}", time());
+        }
+    }
+}
+
+fn time() -> String {
+    let system_time = SystemTime::now();
+    let datetime: DateTime<Utc> = system_time.into();
+    datetime.to_rfc3339()
+}