watch for stdout and stderr

src/main.rs

@@ -10,7 +10,7 @@ use std::error::Error;
 use std::fs::File;
 use std::io::Read;
 use std::path::PathBuf;
-use std::process::{Child, Command, ExitStatus};
+use std::process::{Child, Command, ExitStatus, Stdio};
 
 type SupResult<T> = Result<T, Box<dyn Error>>;
 
@@ -36,24 +36,21 @@ impl App {
 		match command.output() {
 			Ok(output) => {
 				if !output.stdout.is_empty() {
-					info!(
-						"[{}] stdout: {}",
-						&self.name,
-						String::from_utf8(output.stdout)?
-					);
+					let s = String::from_utf8(output.stdout)?;
+					for line in s.lines() {
+						info!("[{}] stdout: {}", &self.name, line);
+					}
 				}
 				if !output.stderr.is_empty() {
-					info!(
-						"[{}] stderr: {}",
-						&self.name,
-						String::from_utf8(output.stderr)?
-					);
+					let s = String::from_utf8(output.stderr)?;
+					for line in s.lines() {
+						info!("[{}] stderr: {}", &self.name, line);
+					}
 				}
+				Ok(())
 			}
-			Err(e) => error!("Error starting app: {}: {:?}", &self.name, e),
+			Err(e) => Err(Box::from(e)),
 		}
-
-		Ok(())
 	}
 }
 
@@ -85,12 +82,56 @@ impl Proc {
 		info!("starting application {}", &app.name);
 
 		let mut command = Command::new(&app.command);
+		command.stdout(Stdio::piped());
+		command.stderr(Stdio::piped());
 		command.args(&app.args);
 
 		let child = command.spawn()?;
 
 		Ok(Proc { app, child })
 	}
+
+	fn check_stdout(&mut self) -> Option<String> {
+		let child_stdout = self.child.stdout.as_mut();
+		if let Some(stdout) = child_stdout {
+			let mut buf = String::new();
+			match stdout.read_to_string(&mut buf) {
+				Ok(size) => {
+					if size > 0 {
+						return Some(buf);
+					} else {
+						return None;
+					}
+				}
+				Err(e) => {
+					error!("couldn't read stdout from {}: {:?}", &self.app.name, e);
+					return None;
+				}
+			}
+		}
+		None
+	}
+
+	fn check_stderr(&mut self) -> Option<String> {
+		let child_stderr = self.child.stderr.as_mut();
+		if let Some(stderr) = child_stderr {
+			let mut buf = String::new();
+			match stderr.read_to_string(&mut buf) {
+				Ok(size) => {
+					if size > 0 {
+						return Some(buf);
+					} else {
+						return None;
+					}
+				}
+				Err(e) => {
+					error!("couldn't read stderr from {}: {:?}", &self.app.name, e);
+					return None;
+				}
+			}
+		}
+		None
+	}
 }
 
 fn main() {
@@ -105,6 +146,7 @@ fn main() {
 	}
 }
 
+#[allow(clippy::cognitive_complexity)]
 fn run() -> SupResult<()> {
 	let config = Config::load("sup.toml")?;
 	info!("loaded config: sup.toml");
@@ -159,12 +201,21 @@ fn run() -> SupResult<()> {
 					}
 				}
 				Ok(None) => {
+					if let Some(s) = &proc.check_stdout() {
+						for line in s.lines() {
+							info!("[{}] stdout: {}", &proc.app.name, line);
+						}
+					}
+					if let Some(s) = &proc.check_stderr() {
+						for line in s.lines() {
+							info!("[{}] stderr: {}", &proc.app.name, line);
+						}
+					}
 					newprocs.push(proc);
 				}
 				Err(e) => error!("error: {:?}", e),
 			}
 		}
-
 		procs = newprocs;
 	}