Print error messages to stderr in quickstart and quick_main.

Author: test9753

examples/quickstart.rs

@@ -21,16 +21,20 @@ use errors::*;
 
 fn main() {
     if let Err(ref e) = run() {
-        println!("error: {}", e);
+        use ::std::io::Write;
+        let stderr = &mut ::std::io::stderr();
+        let errmsg = "Error writing to stderr";
+
+        writeln!(stderr, "error: {}", e).expect(errmsg);
 
         for e in e.iter().skip(1) {
-            println!("caused by: {}", e);
+            writeln!(stderr, "caused by: {}", e).expect(errmsg);
         }
 
         // The backtrace is not always generated. Try to run this example
         // with `RUST_BACKTRACE=1`.
         if let Some(backtrace) = e.backtrace() {
-            println!("backtrace: {:?}", backtrace);
+            writeln!(stderr, "backtrace: {:?}", backtrace).expect(errmsg);
         }
 
         ::std::process::exit(1);

src/quick_main.rs

@@ -36,18 +36,22 @@
 macro_rules! quick_main {
     ($main:expr) => {
         fn main() {
+            use ::std::io::Write;
+            let stderr = &mut ::std::io::stderr();
+            let errmsg = "Error writing to stderr";
+
             ::std::process::exit(match $main() {
                 Ok(ret) => $crate::ExitCode::code(ret),
                 Err(ref e) => {
                     let e: &$crate::ChainedError<ErrorKind=_> = e;
-                    println!("Error: {}", e);
+                    writeln!(stderr, "Error: {}", e).expect(errmsg);
 
                     for e in e.iter().skip(1) {
-                        println!("Caused by: {}", e);
+                        writeln!(stderr, "Caused by: {}", e).expect(errmsg);
                     }
 
                     if let Some(backtrace) = e.backtrace() {
-                        println!("{:?}", backtrace);
+                        writeln!(stderr, "{:?}", backtrace).expect(errmsg);
                     }
 
                     1