25.07.2017

Ingress: Level 16 reached...

After long time playing google/niantic's ingress (the predecessor of pokemon go - all the arenas are portals in ingress, most of them created by ingress players) i reached the last level:



And the usual welcome package:


I am wondering, wether i should continue playing or quit the game for now or ever.
Perhaps reading this discussion (What do lvl 16 players play for?) may help me.

19.07.2017

(bash): The most useless commands (8)


After talking about

  1. rev
  2. yes
  3. sl
  4. cowsay
  5. cmatrix
  6. cal
 i found another funny command:
rig
Its manpage tells the following:
DESCRIPTION
       Rig  is a utility that will piece together a random first name, last name, street num‐
       ber and address, along with a geographically consistant (ie, they all match  the  same
       area) city, state, ZIP code, and area code.

       It is suitable for such applications as feeding the NY times registration page to fend
       off junk (snail) mail and telemarketers, or for registering  on  BBS's  to  which  you
       don't wish to reveal your real information.
I am not sure if this tool is banned by the NSA ;-) but here we go:
schroff@zerberus:~$ rig
Carmelo Suarez
947 East Parson St
Alton, IL  62002
(708) xxx-xxxx
schroff@zerberus:~$ rig
Janna Stewart
970 Potter Rd
Auburn, NY  13021
(315) xxx-xxxx
schroff@zerberus:~$ rig
Bernadine Collins
27 Willow Rd
Seattle, WA  98109
(206) xxx-xxxx

15.07.2017

OpenJDK 9: Jshell - Using Swing / doing GUI stuff

After the posts buitin commands of jshell and how to load and save scripts i tried to get swing components running.

I created a script  HelloWorld.java
import javax.swing.*;       

JFrame frame = new JFrame("HelloWorldSwing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JLabel label = new JLabel("Hello World");
frame.getContentPane().add(label);
frame.pack();
frame.setVisible(true);
But this does not work with Ubuntu:
jshell HelloWorld.java
#
# A fatal error has been detected by the Java Runtime Environment:
#
#  SIGSEGV (0xb) at pc=0x00007f61041bb009, pid=7440, tid=7442
#
# JRE version: OpenJDK Runtime Environment (9.0) (build 9-internal+0-2016-04-14-195246.buildd.src)
# Java VM: OpenJDK 64-Bit Server VM (9-internal+0-2016-04-14-195246.buildd.src, mixed mode, tiered, compressed oops, g1 gc, linux-amd64)
# Problematic frame:
# C  [libjava.so+0x1d009]  JNU_GetEnv+0x19
#
# Core dump will be written. Default location: Core dumps may be processed with "/usr/share/apport/apport %p %s %c %P" (or dumping to /home/schroff/core.7440)
#
# An error report file with more information is saved as:
# /home/schroff/hs_err_pid7440.log
#
# If you would like to submit a bug report, please visit:
#   http://bugreport.java.com/bugreport/crash.jsp
# The crash happened outside the Java Virtual Machine in native code.
# See problematic frame for where to report the bug.
#
|  State engine terminated.
|  Restore definitions with: /reload restore
|  Resetting...
|  Welcome to JShell -- Version 9-internal
|  For an introduction type: /help intro
Hmmm. This does look good.

On a Windows 10 host it works without any problem:


I hope this bug will be fixed soon...
EDIT: After downloading a new version from java.net it worked:

./java -version
java version "9"
Java(TM) SE Runtime Environment (build 9+178)
Java HotSpot(TM) 64-Bit Server VM (build 9+178, mixed mode)


14.07.2017

Bash: enabling Eclipse for Bash Programming | Plugin basheclipse (debugging) part 1

In my last posting i showed how to install the plugin shelled and its configuration options.

Now the next step is to install basheclipse, which enables eclipse in conjunction with shelled to debug bash scripts.

Step 1: Download basheclipse

Step 2: Do not copy the jar file to the plugins directory if you are using Eclipse Neon. Copy them to the dropins directory.

Step 3: Restart eclipse (and wait. I had to wait nearly 5 minutes with a cpu usage of 100%)

Step 4: Change the Shell interpreter in shelled (->window->preferences->shell script->interpreters):

Step  5: Create a new Shell Script Project:
 


 Step 6: Create a Shell Script File:

Step 7: Copy _DEBUG.sh into your project directory
Step 8: Add _DEBUG.sh at the beginning of your file with full qualified directory name:
 ~/devel/workspace/MyShellScriptProjekct/_DEBUG.sh
Step 9: Go to ->run->debug configurations and create a new configuration inside "bash script"
 You have to select your scriptfile here:
But after doing all this steps i was not able to set breakpoints.
I tried
  • java 1.5 with
    Eclipse Juno


    But this did not work.
  • java 1.9 with
    Eclipse Neon


    Did neither work (this posting)

But: Java 1.6 with Eclipse Luna works!


Read the next posting how to debug a bash scripts in eclipse...

EDIT: After changing from OpenJDK to Oracle's JDK it even works with Eclipse Neon.

OpenJDK 9: Jshell - how to load scripts and how to save/persist finished snippets

In my last posting i showed the builtin jshell commands and how to start working with the java shell.

What about loading and saving scripts?

I created a file myshell.txt with this content:
class MyClass {
 private int a;
 public MyClass(){a=0;}
 int getA() {return a;};
 void setA(int var) {a=var; return;}
}
MyClass ZZ;
ZZ = new MyClass();
ZZ.setA(200);
The help shows the following:
-> /help /open

|  /open

|  Open a file and read its contents as snippets and commands.

|  /open
|      Read the specified file as jshell input.
so i tried this one:
-> /open myjshell.txt
hmmm. No feedback inside jshell. But no news is good news:
-> /list

   1 : class MyClass {
        private int a;
        public MyClass(){a=0;}
        int getA() {return a;};
        void setA(int var) {a=var; return;}
       }
   2 : MyClass ZZ;
   3 : ZZ = new MyClass();
   4 : ZZ.setA(200);
 Saving your work is quite easy:
-> /help /save

|  /save

|  Save the specified snippets and/or commands to the specified file.

|  /save
|      Save the source of current active snippets to the file.

|  /save all
|      Save the source of all snippets to the file.
|      Includes source including overwritten, failed, and start-up code.

|  /save history
|      Save the sequential history of all commands and snippets entered since jshell was launched.

|  /save start
|      Save the default start-up definitions to the file.
And also no news is good news:
-> /save myjshell2.txt
and like expected:
$ cat myjshell2.txt
class MyClass {
 private int a;
 public MyClass(){a=0;}
 int getA() {return a;};
 void setA(int var) {a=var; return;}
}
MyClass ZZ;
ZZ = new MyClass();
ZZ.setA(200);
But what about this /save start ?
-> /save start myjshell3.txt
and the content of this file is:
$ cat myjshell3.txt

import java.util.*;
import java.io.*;
import java.math.*;
import java.net.*;
import java.util.concurrent.*;
import java.util.prefs.*;
import java.util.regex.*;
void printf(String format, Object... args) { System.out.printf(format, args); }
 To load a scipt on startup just type
jshell myjshell.txt



12.07.2017

OpenJDK 9: JShell - an interactive java interpreter shell | builtin commands

One of the new features of java 9 is jshell (JEP 222).

On my ubuntu system the installation was quite easy:
# apt-get install openjdk-9-jdk-headless
and you can find
$ ls /usr/lib/jvm/java-9-openjdk-amd64/bin/
idlj       jcmd    jmap        jstatd       schemagen
jar        jdb     jmod        keytool      serialver
jarsigner  jdeps   jps         orbd         servertool
java       jhsdb   jrunscript  pack200      tnameserv
javac      jimage  jsadebugd   policytool   unpack200
javadoc    jinfo   jshell      rmic         wsgen
javah      jjs     jstack      rmid         wsimport
javap      jlink   jstat       rmiregistry  xjc
 (in the third column, sixth row: jshell)

After a startup jshell comes up with this prompt:

$ /usr/lib/jvm/java-9-openjdk-amd64/bin/jshell
|  Welcome to JShell -- Version 9-internal
|  For an introduction type: /help intro


->
 The most important command is
/exit
to leave the jshell (Strg-C works also, but i think /exit should be used).

There is no syntax highlighting but this does not matter.

The following builtin commands are allowed:
-> /help
|  Type a Java language expression, statement, or declaration.
|  Or type one of the following commands:

|     /list [all|start|]                       -- list the source you have typed
|     /edit                                    -- edit a source entry referenced by name or id
|     /drop                                    -- delete a source entry referenced by name or id
|     /save [all|history|start]                      -- Save snippet source to a file.
|     /open                                          -- open a file as source input
|     /vars                                                -- list the declared variables and their values
|     /methods                                             -- list the declared methods and their signatures
|     /classes                                             -- list the declared classes
|     /imports                                             -- list the imported items
|     /exit                                                -- exit jshell
|     /reset                                               -- reset jshell
|     /reload [restore] [quiet]                            -- reset and replay relevant history -- current or previous (restore)
|     /classpath                                     -- add a path to the classpath
|     /history                                             -- history of what you have typed
|     /help [|]                          -- get information about jshell
|     /set editor|start|feedback|newmode|prompt|format ... -- set jshell configuration information
|     /? [|]                             -- get information about jshell
|     /!                                                   -- re-run last snippet
|     /                                                -- re-run snippet by id
|     /-                                                -- re-run n-th previous snippet

|  For more information type '/help' followed by the name of command or a subject.
|  For example '/help /list' or '/help intro'.  Subjects:

|     intro     -- an introduction to the jshell tool
|     shortcuts -- a description of shortcuts
With /list the source code, which you provided, is shown:
-> /list 5

   5 : class MyClass {
       private int a;
       public MyClass(){a=0;}
       int getA() {return a;};
       void setA(int var) {a=var; return;}
       }

Everytime you create an Object, you will see the following:
-> ZZ = new MyClass();
|  Variable ZZ has been assigned the value MyClass@28d25987

-> ZZ.getA();
|  Expression value is: 0
|    assigned to temporary variable $8 of type int

-> ZZ.setA(200);

-> ZZ.getA();
|  Expression value is: 200
|    assigned to temporary variable $10 of type int
With /vars the variables are shown:
-> /vars
|    MyClass ZZ = MyClass@28d25987
|    int $8 = 0
|    int $10 = 200
Listing the classes (ok it is getting boring):
-> /classes
|    class MyClass
 and last but not least /methods:
-> /methods
|    printf (String,Object...)void
|    getA ()int

10.07.2017

Bash: enabling Eclipse for Bash Programming | Plugin Shelled (shell editor)

After writing several posts about useless shell commands i tried to enable Eclipse for working with the bourne again shell.

First step is to get a plugin for syntax highlighting. The plugin shelled
https://sourceforge.net/projects/shelled/
is very easy to find. Just download the zip

and in Eclipse go to "help --> install new software".
There you have to add the archive:
And all other clicks are straight forward:





After the installation of the plugin you have to restart your Eclipse IDE and then the editor understands bash commands:


The configuration can be done via -> window -> preferences

If you want to setup your own coloring scheme, you can customize it within -> Shell Script -> Editor -> Syntax coloring




To enable bash debugging read this posting.

01.07.2017

(bash): The most useless commands (7)


After talking about
  1. rev
  2. yes
  3. sl
  4. cowsay
  5. cmatrix
here another pretty useless command:
cal
Today with every smartphone having its own calendar app or every e-mail program with integrated time planning function this command is no more needed. The manpage says:
NAME
     cal, ncal — displays a calendar and the date of Easter
And here we go:
$ cal 2000
                            2000
       Januar               Februar                 März        
So Mo Di Mi Do Fr Sa  So Mo Di Mi Do Fr Sa  So Mo Di Mi Do Fr Sa
                   1         1  2  3  4  5            1  2  3  4
 2  3  4  5  6  7  8   6  7  8  9 10 11 12   5  6  7  8  9 10 11
 9 10 11 12 13 14 15  13 14 15 16 17 18 19  12 13 14 15 16 17 18
16 17 18 19 20 21 22  20 21 22 23 24 25 26  19 20 21 22 23 24 25
23 24 25 26 27 28 29  27 28 29              26 27 28 29 30 31  
30 31                                                          
       April                  Mai                   Juni        
So Mo Di Mi Do Fr Sa  So Mo Di Mi Do Fr Sa  So Mo Di Mi Do Fr Sa
                   1      1  2  3  4  5  6               1  2  3
 2  3  4  5  6  7  8   7  8  9 10 11 12 13   4  5  6  7  8  9 10
 9 10 11 12 13 14 15  14 15 16 17 18 19 20  11 12 13 14 15 16 17
16 17 18 19 20 21 22  21 22 23 24 25 26 27  18 19 20 21 22 23 24
23 24 25 26 27 28 29  28 29 30 31           25 26 27 28 29 30  
30                                                              
        Juli                 August              September      
So Mo Di Mi Do Fr Sa  So Mo Di Mi Do Fr Sa  So Mo Di Mi Do Fr Sa
                   1         1  2  3  4  5                  1  2
 2  3  4  5  6  7  8   6  7  8  9 10 11 12   3  4  5  6  7  8  9
 9 10 11 12 13 14 15  13 14 15 16 17 18 19  10 11 12 13 14 15 16
16 17 18 19 20 21 22  20 21 22 23 24 25 26  17 18 19 20 21 22 23
23 24 25 26 27 28 29  27 28 29 30 31        24 25 26 27 28 29 30
30 31                                                          
      Oktober               November              Dezember      
So Mo Di Mi Do Fr Sa  So Mo Di Mi Do Fr Sa  So Mo Di Mi Do Fr Sa
 1  2  3  4  5  6  7            1  2  3  4                  1  2
 8  9 10 11 12 13 14   5  6  7  8  9 10 11   3  4  5  6  7  8  9
15 16 17 18 19 20 21  12 13 14 15 16 17 18  10 11 12 13 14 15 16
22 23 24 25 26 27 28  19 20 21 22 23 24 25  17 18 19 20 21 22 23
29 30 31              26 27 28 29 30        24 25 26 27 28 29 30
                                            31                    
 Or "the date of Easter":
$ ncal -e 2018
 1 April 2018