SIGTERM is now a thing but there's no use of it

assets/disk0/returnany.js

@@ -0,0 +1,3 @@
+println("This program attemps to read a string and returns it verbatim. If the underlying shell is not insane, errorlevel must be 0.\nNow, let's put this to the test...");
+print("Your word? ");
+return read();

assets/disk0/tvdos/TVDOS.SYS

@@ -1,3 +1,19 @@
+// define exceptions
+function InterruptedException(m) {
+    this.message = m;
+    this.stack = (new Error()).stack;
+};
+InterruptedException.prototype = Object.create(Error.prototype);
+InterruptedException.prototype.name = 'InterruptedException';
+InterruptedException.prototype.constructor = InterruptedException;
+class SIG {
+    constructor(name, number) {
+        this.name = "SIG" + name;
+        this.number = number|0;
+    }
+}
+const SIGTERM = new SIG("TERM",15);
+const SIGSEGV = new SIG("SEGV",11)
 // define TVDOS
 var _TVDOS = {};
 _TVDOS.VERSION = "1.0";
@@ -127,20 +143,24 @@ var GL = eval(filesystem.readAll("A"));
 // @param cmdsrc JS source code
 // @param args arguments for the program, must be Array, and args[0] is always the name of the program, e.g.
 //        for command line 'echo foo bar', args[0] must be 'echo'
+// @return status returned by the program
 var execApp = (cmdsrc, args) => {
     var execAppPrg = eval(
-`function InterruptedException(m){this.message=m;this.stack=(new Error()).stack;};` +
-`InterruptedException.prototype=Object.create(Error.prototype);` +
-`InterruptedException.prototype.name='InterruptedException';` +
-`InterruptedException.prototype.constructor=InterruptedException;` +
-`var _appStub=function(exec_args){${cmdsrc}
-};try {_appStub;}
-catch (e){
-    if (e instanceof InterruptedException) 'SIGTERM';
-    else 1;
-}`); // making 'exec_args' a app-level global
+`var _appStub=function(exec_args){${cmdsrc}\n};_appStub`); // making 'exec_args' a app-level global
 
-    return execAppPrg(args);
+    var status = 0;
+
+    try {
+        status = execAppPrg(args);
+        return status;
+    }
+    catch (e) {
+        serial.printerr(`app execution interrupted -- ${e}\n${e.stack}`);
+        if (e instanceof InterruptedException)
+            return SIGTERM;
+        else
+            return (undefined == status) ? 0 : status;
+    }
 }
 
 ///////////////////////////////////////////////////////////////////////////////

assets/disk0/tvdos/bin/command.js

@@ -386,7 +386,7 @@ shell.execute = function(line) {
                 sendLcdMsg(_G.shellProgramTitles[_G.shellProgramTitles.length - 1]);
                 //serial.println(_G.shellProgramTitles);
 
-                return (ret == undefined) ? 0 : ret;
+                return ret;
             }
         }
     }
@@ -457,8 +457,14 @@ if (goInteractive) {
                 try {
                     errorlevel = 0; // reset the number
                     errorlevel = shell.execute(cmdbuf);
-                    //if (isNaN(errorlevel)) errorlevel = 2;
-                    serial.printerr(`errorlevel: ${errorlevel}`);
+                    let rawE = errorlevel;
+
+                    if (errorlevel instanceof SIG)
+                        errorlevel = errorlevel.name;
+                    else if (errorlevel == undefined || (typeof errorlevel.trim == "function" && errorlevel.trim().length == 0) || isNaN(errorlevel))
+                        errorlevel = 0;
+
+                    serial.printerr(`errorlevel: ${errorlevel} (raw: ${rawE})`);
                 }
                 catch (e) {
                     printerrln("\n"+(e.stack || e));