Doc updates

Author: Tilmann Zäschke

README.md

@@ -1,6 +1,6 @@
 # JPAN Command Line Tool
 
-A tool that allows echo, traceroute, showpaths, ... and other functionality, similar to
+A tool that allows `echo`, `traceroute`, `showpaths`, ... and other functionality, similar to
 to the [SCION CLI tool](https://docs.scion.org/en/latest/command/scion/scion.html).
 JPAN-CLI is stand-alone and does not require any locally installed SCION software. 
 
@@ -18,7 +18,7 @@ JPAN-CLI provides several tools:
 
 * `jpan-cli version` - Show the SCION version information
 
-## Execution
+## Usage
 
 All tools can be run from the executable jar file which is available in
 the [GitHub Releases section](https://github.com/netsec-ethz/jpan-cli/releases/download/v0.1.0/jpan-cli.jar).

src/main/java/org/scion/cli/Cli.java

@@ -247,12 +247,16 @@ static void printUsageShowpaths() {
     println("'showpaths' lists available paths between the local and the specified");
     println("SCION AS.");
     println("");
-    println("By default, the paths are probed. Paths served from the SCION Daemon's might not");
-    println("forward traffic successfully (e.g. if a network link went down, or there is a black");
-    println("hole on the path). To disable path probing, set the appropriate flag.");
-    println("");
-    println("If no alive path is discovered, json output is not enabled, and probing is not");
-    println("disabled, showpaths will exit with the code 1.");
+    println("Path probing: Unlike `scion`, jpan-cli does no path probing."); // TODO
+    //    println("By default, the paths are probed. Paths served from the SCION Daemon's might
+    // not");
+    //    println("forward traffic successfully (e.g. if a network link went down, or there is a
+    // black");
+    //    println("hole on the path). To disable path probing, set the appropriate flag.");
+    println("");
+    //    println("If no alive path is discovered, json output is not enabled, and probing is not");
+    //    println("disabled, showpaths will exit with the code 1.");
+    println("If no alive path is discovered, showpaths will exit with the code 1."); // TODO
     println("On other errors, showpaths will exit with code 2.");
     //    println("");
     //    printSequenceHelp();
@@ -266,13 +270,14 @@ static void printUsageShowpaths() {
     println("");
     println("Examples:");
     println("  jpan-cli showpaths 1-ff00:0:110 --extended");
-    println("  jpan-cli showpaths 1-ff00:0:110 --local 127.0.0.55 --json");
-    println("  jpan-cli showpaths 1-ff00:0:111 --sequence=\"0-0#2 0*\" # outgoing IfID=2");
-    println(
-        "  jpan-cli showpaths 1-ff00:0:111 --sequence=\"0* 0-0#41\" # incoming IfID=41 at dstIA");
-    println(
-        "  jpan-cli showpaths 1-ff00:0:111 --sequence=\"0* 1-ff00:0:112 0*\" # 1-ff00:0:112 on the path");
-    println("  jpan-cli showpaths 1-ff00:0:110 --no-probe");
+    // println("  jpan-cli showpaths 1-ff00:0:110 --local 127.0.0.55 --json");
+    // println("  jpan-cli showpaths 1-ff00:0:111 --sequence=\"0-0#2 0*\" # outgoing IfID=2");
+    // println(
+    //    "  jpan-cli showpaths 1-ff00:0:111 --sequence=\"0* 0-0#41\" # incoming IfID=41 at dstIA");
+    // println(
+    //     "  jpan-cli showpaths 1-ff00:0:111 --sequence=\"0* 1-ff00:0:112 0*\" # 1-ff00:0:112 on
+    // the path");
+    // println("  jpan-cli showpaths 1-ff00:0:110 --no-probe");
     println("");
     println("Flags:");
     //    println("      --epic                   Enable EPIC.");

src/main/java/org/scion/cli/Showpaths.java

@@ -108,7 +108,7 @@ private static void parseArgs(String[] argsArray) {
     }
   }
 
-  public static int run() throws IOException {
+  public static void run() throws IOException {
     ScionService service = Scion.defaultService();
     // dummy address
     InetSocketAddress destinationAddress =
@@ -150,7 +150,11 @@ public static int run() throws IOException {
         println(header + compact);
       }
     }
-    return paths.size();
+
+    if (paths.isEmpty()) {
+      throw new ExitCodeException(
+          1, "No paths found to destination: " + ScionUtil.toStringIA(isdAs));
+    }
   }
 
   private static void printExtended(Path path, String localIP) {