Mr N

Here are a few Maven things I want to remember:

If you want to download all the source jars in a project:

mvn dependency:resolve -Dclassifier=sources

Print dependencies:

mvn dependency:tree

This is a great one. The colouring of the circle bands, tricks your eyes into thinking that the circle starts at different places.

I had a look for the original source but it's copied across Twitter and Redit. Couldn't find anything else.

All the balls are the same colour!

Credit: Derren Brown linked to Daniell Owengrub's blog which linked to SyFy which linked to David Novick (creator of image)

I spent ages trying to get Orca to read selected text but there are a mind boggling number of options and while the GNOME (Ubuntu's default desktop manager) documentation is pretty good it never really worked. On further reading there seems to be some issue with Firefox and it was unclear if this had been resolved. I could get the Accessibility Options box to pop up using the short cut keys but none of the key bindings seemed to work for me. It's a shame because Orca comes with all sorts of goodies like reading mnemonics as text, reading camel case words as separate words (very handy if you read a lot of technical documentation!). Anyway, I couldn't get it to work so found another solution; not quite as feature rich but it does exactly what i want.

You need 2 pieces of software installed: something to read selected text (xsel) and something to read it out (espeak`) so install both of those:

sudo apt install espeak xsel

To test xsel is working:

1. Open a terminal window.
2. Use your mouse to highlight some text in the window.
3. Type: xsel. Your selected text should be returned by the command.

To test espeak is working just type:

echo "MrN is Ace" | espeak

and it should read out what is true ;)

Now we just need to put that together. Under GNOME (other Desktop managers may do it differently) we'll create a shortcut key binding to run our command on a magic key combo.

1. Open Settings application.
2. Go to Devices.
3. Go to Keyboard.
4. Go down to the bottom and click +.
5. Enter a name as "Read selected text".
6. Enter command as:

   bash -c "xsel | sed -e :a -e '$!N;s/\n/ /;ta'| espeak"
   

7. Click shortcut then make the key combination. I use CMD+[ on my Mac so Win+[ seemed simple on my PC.
8. On my Mac the read-text command is a toggle as it's built in. This is not the case when just running a command. I should probably put the read text command into a script so it can detect if it's already running, restart it etc, but that can be a job for another day. For the moment I just need to get up and running, so we'll create something that kills espeak. So create another entry by hitting the + button.
9. Enter a name as "Stop read selected text".
10. Enter command as:

    bash -c "kill `ps -au | grep '[0-9] espeak$' | awk '{print $2}'`"
    

11. In this case I just picked the bracket next to it as it has the least impact on muscle memory.

That's it, it works in the text editor, browsers and everywhere else. Some browsers use CSS to stop you selecting the text but if you press F7 it'll switch on caret mode which lets you highlight text again. In applications (not web browsers) this is off my default but you should be able to toggle it with F7 too.

This is a tutorial and example of how Bash increases productivity.

We know that a Java archive is just a zip archive so it contains lots of files. We want to create our own index of what they contain so we are going to unpack them and create an index of their contents. Here is the situation.

$ ls -l
total 48616
-rwxr-xr-x 1 davidnewcomb staff 12952991 28 Nov 13:57 MRN.ear
-rwxr-xr-x 1 davidnewcomb staff 11642532 15 Sep 2017 MRN.war
-rwxr-xr-x 1 davidnewcomb staff 289943 21 May 2018 client.jar

Let's practice with one to start with. The Java comes with a jar program to help you play with the file format. First we need a folder name:

file="MRN.ear"
dir=`echo $file | sed 's/\./_/'`

This writes a line with MRN.ear into the pipe, sed takes each line and looks for a period followed by everything and replaces it with nothing. The result is assigned to a variable called dir.

Next we are going to do the work using our new variable. First make a directory:

mkdir $dir

Then go into it:

mkdir $dir ; cd $dir

Next unpack the archive, we have to remember that we are actually a directory below the location of the archive so we need to prefix ../ to the path.

mkdir $dir ; cd $dir ; tar -xf ../$file

Finally we need to make the archive catalogue. So back up a directory level find what we want:

mkdir $dir ; cd $dir ; tar -xf ../$file ; cd .. ; find $dir > $dir.find.txt

That'll work with one of them, but we have hundreds! No problem, we can just wrap it all in a loop.

for file in `ls`; do dir=`echo $file | sed 's/\./_/'` ; mkdir $dir ; cd $dir ; tar -xf ../$file ; cd .. ; find $dir > $dir.find.txt ; done

for runs once for each item in a white space (or line break) separated list. We are running ls to generate the list. Each item in the list will be assigned to $file and then we just follow our normal path from before.

We have some choices now depending on what kind of resources you have. Bash has the amazing ability to run tasks in the background so waiting for a long command to complete just means you can do something else for a bit! You can push a task into the background by adding an ampersand to the end. For one command it's

echo "hello" &

or we can chain them together like so:

(cat /etc/hosts | grep 127) &
(cd bin ; ls) &

Let's add that to our command:

for file in `ls`; do (dir=`echo $file | sed 's/\./_/'` ; mkdir $dir ; cd $dir ; tar -xf ../$file ; cd .. ; find $dir > $dir.find.txt ) & done

There's no need for a semi-colon at the end because the closing parenthesis marks the end of the statement too so we can drop it.

It can be a bit tricky to write all of this first time and get it all right so there are various little tricks you can do while you are trying. Firstly write protect our starting files, we don't want to overwrite them by mistake:

chmod -w *

In the for loop I would create an expression that just produces one result. So you could try either of these:

for file in `ls | head -1`
for file in MRN.ear

Also you want to start from a clean slate each time, so remove anything with an underscore in it or anything ending with .txt:

rm -rf *_* *.txt ; for file in `ls | head -1`

When we think we have got it right then remove the |head -1 and run it for real.

I've talked it through in terms of the mental thought processes behind building the command so it has taken a bit longer to go through it. When you work in this environment, it's not long before you start to think in terms of running commands together using the background with lots of piping to get what you want. It becomes second nature, you can do some incredible things. Sometimes those lines will go into a bigger bash program or used in a scheduled task, but most of the time, surprisingly, they are just thrown away because that thing you wanted to do is now done and you won't have to do it again. It's not even worth putting it in a file!!!