--- a/src/command.rs	Sun Nov 01 12:52:13 2020 +0900
+++ b/src/command.rs	Sun Nov 01 14:02:35 2020 +0900
@@ -10,15 +10,17 @@
 }
 
 pub fn start_command(user_name: &'static str, vm_name: String) {
+    virsh::command_require_vm_name(get_vm_name(user_name, vm_name), "start");
+}
+
+fn get_vm_name(user_name: &'static str, vm_name: String) -> String {
     let vm_name = match vm_name.parse::<u8>() {
         Ok(_) => format!("{}-{}", user_name, vm_name),
         Err(_) => vm_name,
     };
 
-    let vm_name = if vm_name.starts_with(user_name) {
-        vm_name
-    } else {
-        format!("{}-{}", user_name, vm_name)
-    };
-    virsh::start_vm(vm_name);
+    if vm_name.starts_with(user_name) {
+        return vm_name;
+    }
+    format!("{}-{}", user_name, vm_name)
 }

--- a/src/virsh.rs	Sun Nov 01 12:52:13 2020 +0900
+++ b/src/virsh.rs	Sun Nov 01 14:02:35 2020 +0900
@@ -31,12 +31,12 @@
     )
 }
 
-pub fn start_vm(vm_name: String) {
+pub fn command_require_vm_name(vm_name: String, operation: &str) {
     let output = Command::new("virsh")
-        .arg("start")
+        .arg(operation)
         .arg(vm_name)
         .output()
-        .expect("failed to start vm");
+        .unwrap_or_else(|_| panic!("failed to {}", operation));
 
     io::stdout().write_all(&output.stdout).unwrap();
     io::stderr().write_all(&output.stderr).unwrap();