added terminal check

src/error.rs

@@ -30,3 +30,8 @@ pub fn missing_target() {
 	exit(4);
 }
 
+pub fn not_terminal() {
+	println!("remux: not running from a terminal");
+	exit(5);
+}
+

src/main.rs

@@ -1,3 +1,4 @@
+use std::io::{ stdout, IsTerminal };
 
 use pico_args::Arguments;
 
@@ -13,6 +14,8 @@ fn main() {
 		return;
 	}
 
+	if !stdout().is_terminal() { error::not_terminal(); }
+
 	let subcommand = args.subcommand().unwrap();
 
 	match subcommand.as_deref() {