This is a ten second assignment if you know what you are doing. If this seems very new to you, it may take as long as 30 minutes. If you do not get it in that time, arrange to see me before noon on Wednesday.

1. Type, echo $PATH, at the command line. The $ is important, because as with Perl, it tells the shell that we are referencing a variable and want its value, not the literal string, PATH. In this case, PATH is an evironment variable that is set when you launch a new shell, because the shell program (bash) configures itself by reading a number of config files including your .bashrc file. Note that the response from typing, echo $PATH, is a list (colon separated) of directors on bob. In those directories are found the command shell commands we use such as ls, cd, etc.
In fact, any command you type at the shell must be in one of the directories in this list or the shell will not be able to find and run it. For example, if you type, dummycommand, the shell will report an error saying that it cannot find that command. Each "command" is simply a program that bob knows how to run. It can be a standalone program compiled down to machine code that runs natively on bobs hardware or it can be a Perl, Python, Java or some other type of program that is interpreted in one fashion or another through some intermediary program (i.e. Perl, Python, or the Java virtual machine).

2. Now type, java -version. This command will display the version of Java that your shell uses by default when you compile or run Java code. Note that the default version is java 1.4.x. When you type java or javac at the command line, the shell executes programs by that name. By default, on bob, those programs work with version 1.4.x of Java. Based on the discussion above, determine exactly what program is being run by the shell when you type, java. Send me an email with your answer.
3. In order to make our development of a web crawler easier, we will work with version 1.5 of Java. An easy way to do this is to change our shell environment so that when we use any Java commands (i.e. java or javac), the shell knows to use the version 1.5 commands. It turns out that bob has both 1.4 and 1.5 Java JDK/JREs. In order to make the shell use the 1.5 JDK when we type java, we need to update our shell environment variable with the location of the 1.5 JDK binaries. The 1.5 binaries can be found in the directory /opt/jdk1.5.0/bin. Do a directory listing to see what is in that directory. Note that you find java, javac, javadoc, and others. Edit your .bashrc file and add a line to add /opt/jdk1.5.0/bin to your PATH environment variable. Make certain that you simply add another directory to the PATH variable instead of completely changing the value of the PATH variable. Three things are important to note, in order to do this correctly. 1) Multiple directories are separated by colons in a PATH variable. 2) You can access the current value of the PATH variable using $PATH. 3) Directories listed first in the value of PATH will be searched first for commands matching what you type at the command line. Your changes will not take effect until your .bashrc is read by the shell. The easiest way to force this is by typing, source .bashrc at the command line. The first command found that matches a name is the one that is executed. If you complete this portion of the assignment correctly, when you type echo $PATH you will see the new 1.5 JDK bin directory in your PATH.