Java™ Application Development on Linux - Dator

1.3 Basic Linux Concepts and Commands25where myscript is the name of the file in which you have put your commands.(See Chapter 2 for more on how to do that.) Once you’ve got a script runningthe way you’d like, you might want to make its invocation as seamless as anyother command. To do that, change its permissions to include the executionpermission and then, if the file is located in a place that your PATH variableknows about, it will run as a command. Here’s an example:$ chmod a+rx myscript$ mv myscript ${HOME}/bin$ myscript... (script runs)$The file was put into the bin directory off of the home directory. That’sa common place to put homebrew commands. Just be sure that $HOME/bin isin your PATH, or edit .bashrc and add it.If you want to parameterize your shell, you’ll want to use the variables $1,$2, and so on which are given the first, second, and so on parameters on thecommand line that you used to invoke your script. If you type myscriptAccount.java then $1 will have the value Account.java for that invocationof the script.We don’t have the space to go into all that we’d like to about shell programming,but let us leave you with a simple example that can show you someof its power. Used in shell scripts, for loops can take a lot of drudgery out offile maintenance. Here’s a simple but real example.Imagine that your project has a naming convention that all Java files associatedwith the user interface on your project will begin with the letters “UI”.Now suppose your boss decides to change that convention to “GUI” but you’vealready created 200 or more files using the old naming convention. Shell scriptto the rescue:for i in UI*.javadonew="G${i}"echo $i ' ==> ' $newmv $i $newdoneYou could just type those commands from the command line—that’s thenature of shell syntax. But putting them into a file lets you test out the scriptwithout having to type it over and over, and keeps the correct syntax once