Add warning to vpv if no input is given

Cargo.toml

@@ -76,6 +76,7 @@ signal-hook = "0.1.8"
 [dev-dependencies]
 rand = "0.6.5"
 pretty-bytes = "0.2.2"
+atty = "0.2.11"
 
 [features]
 blt-backend = ["bear-lib-terminal"]

examples/vpv.rs

@@ -1,6 +1,3 @@
-extern crate cursive;
-extern crate pretty_bytes;
-
 use std::io;
 
 use cursive::traits::{Boxable, With};
@@ -25,7 +22,7 @@ fn main() {
     let start = time::Instant::now();
 
     // If an argument is given, it is the file we'll read from.
-    // Else, read from stdin.
+    // Otherwise, read from stdin.
     let (source, len) = match std::env::args().nth(1) {
         Some(source) => {
             let meta = std::fs::metadata(&source).unwrap();
@@ -36,41 +33,11 @@ fn main() {
         None => (None, None),
     };
 
-    // Start the copy in a separate thread
-    thread::spawn(move || {
-        // Copy to stdout - lock it for better performance.
-        let stdout = io::stdout();
-        let mut stdout = stdout.lock();
-
-        match source {
-            None => {
-                // Copy from stdin - lock it for better performance.
-                let stdin = io::stdin();
-                let stdin = stdin.lock();
-                let mut reader =
-                    utils::ProgressReader::new(counter_copy, stdin);
-
-                // And copy!
-                io::copy(&mut reader, &mut stdout).unwrap();
-            }
-            Some(source) => {
-                // Copy from stdin - lock it for better performance.
-                let input = std::fs::File::open(source).unwrap();
-                let mut reader =
-                    utils::ProgressReader::new(counter_copy, input);
-
-                // And copy!
-                io::copy(&mut reader, &mut stdout).unwrap();
-            }
-        }
-
-        // When we're done, shut down the application
-        cb_sink.send(Box::new(|s: &mut Cursive| s.quit())).unwrap();
-    });
-
     // Add a single view: progress status
     siv.add_layer(
-        Dialog::new().title("Copying...").content(
+        Dialog::new()
+            .title("Copying...")
+            .content(
                 LinearLayout::vertical()
                     .child(
                         Canvas::new(counter.clone())
@@ -87,7 +54,8 @@ fn main() {
                                 // Print ETA if we have a file size
                                 // Otherwise prints elapsed time.
                                 if let Some(len) = len {
-                                let remaining = (len as f64 - ticks) / speed;
+                                    let remaining =
+                                        (len as f64 - ticks) / speed;
                                     printer.print(
                                         (0, 0),
                                         &format!(
@@ -125,10 +93,53 @@ fn main() {
                             );
                         }
                     }),
-        ),
+            )
+            .button("Abort", Cursive::quit),
     );
 
+    if source.is_none() && atty::is(atty::Stream::Stdin) {
+        siv.add_layer(
+            Dialog::text(
+                "Please specify an input file or redirect a file to stdin.
+
+cargo run --example vpv </dev/zero >/dev/null",
+            )
+            .button("Quit", Cursive::quit),
+        );
+    } else {
+        // Start the copy in a separate thread
+        thread::spawn(move || {
+            // Copy to stdout - lock it for better performance.
+            let stdout = io::stdout();
+            let mut stdout = stdout.lock();
+
+            match source {
+                None => {
+                    // Copy from stdin - lock it for better performance.
+                    let stdin = io::stdin();
+                    let stdin = stdin.lock();
+                    let mut reader =
+                        utils::ProgressReader::new(counter_copy, stdin);
+
+                    // And copy!
+                    io::copy(&mut reader, &mut stdout).unwrap();
+                }
+                Some(source) => {
+                    // Copy from stdin - lock it for better performance.
+                    let input = std::fs::File::open(source).unwrap();
+                    let mut reader =
+                        utils::ProgressReader::new(counter_copy, input);
+
+                    // And copy!
+                    io::copy(&mut reader, &mut stdout).unwrap();
+                }
+            }
+
+            // When we're done, shut down the application
+            cb_sink.send(Box::new(|s: &mut Cursive| s.quit())).unwrap();
+        });
         siv.set_autorefresh(true);
+    }
 
     siv.run();
 }