Using the zlog to keep track of the 6.170 zephyr instance

Why use the zlog?

The zephyr instance is an active discussion group for questions and answers regarding 6.170: about the problem sets, about the course material (proper specification, testing strategies, etc.), about the intricacies of the Java language and libraries (semantics and implementation details) as they relate to the course, and so on.

However, since the instance is often high traffic, the constant stream of zephyrs can be distracting. Also, some students spend time OFFLINE (!), and thus can't benefit from the discussions taking place on the instance in real time.

The 6.170 zlog is a solution to these two problems. It logs every message sent on the 6.170 zephyr instance. This way, you can unsubscribe from the instance and read the conversations that others are having on the instance seperately, on your own time and at your own pace. You can also review conversations that took place while you were logged off. It is often very useful to skim the log before starting the problem set, just to check if there are any common problems with the Java runtime that other students are encountering and prepare to handle them yourself.

How to use the zlog

The 6.170 zlog is stored in the zlog locker on athena. To access it, first type at the athena prompt: athena% add zlog The 6.170 zlog is in the file /mit/zlog/6.170

The zlog is a text file like any other. Therefore, you could try opening it in your favorite text browser. However, it can grow very large, which makes navigating the messages difficult.

Thus, it is recommended that you try the tail command as an alternate way of reading the zlog. The tail command is similar to the cat and head commands in Unix, except that instead of starting at the beginning of a file and printing the successive lines, it starts at some point near the end of a file and then prints the remainder of the file to the terminal. This way you don't have to scroll through pages of zephyrs you saw the last time you were logged in; you just see the last few ones that were sent.

You can tell tail to start at an arbitrary offset from the end or the beginning of the file; the default action of

athena% tail /mit/zlog/6.170

is to print the last ten lines of the zlog. To have it start further back, pass the -number option to tail, where number is the number of lines to offset the starting point from the end of the file. So,

athena% tail -50 /mit/zlog/6.170

outputs the last 50 lines of the log.

You can even have tail wait and print out new zephyrs as they come in, if you prefer not to mix the 6.170 instance conversations with your personal zephyr conversations. To do this, use the -f option, as in:

athena% tail -f /mit/zlog/6.170

For more information on tail, it is recommended that you read the man page, by typing at the athena prompt:

athena% man tail