fix: throw an error when try to view a directory

CHANGELOG.md

@@ -1,3 +1,9 @@
+# unreleased
+
+## Bugfixes
+
+- Throw an error when try to view a directory, see #234 (@Integral-Tech)
+
 # v0.15.0
 
 ## Features

src/main.rs

@@ -234,7 +234,14 @@ fn run() -> Result<()> {
     let stdin = io::stdin();
 
     let mut reader = match opt.file {
-        Some(filename) => Input::File(File::open(filename)?),
+        Some(filename) => {
+            let file = File::open(&filename)?;
+            if file.metadata()?.is_dir() {
+                return Err(anyhow!("{} is a directory.", filename.display()));
+            }
+
+            Input::File(file)
+        }
         None => Input::Stdin(stdin.lock()),
     };