Tip: Use a Batch File to View Today’s System Log

Once a JNIOR is up and running in an application it rarely needs attention. In fact many users forget that it is even there. It is however good practice to check the system logs once and a while. Fortunately there are a number of ways that you can do that. If you open the DCP (Dynamic Configuration Pages) by accessing the unit with a browser there is a ‘Syslog’ tab. This displays the log with the most recent events right at the top. You can also go to the ‘Console’ tab or otherwise open the Command Line through a Telnet connection or the serial port where you can list the log content directly to the screen or window. In this case the latest entries are the last listed.

If you are developing a new application and testing it on the JNIOR you may wish to monitor the log more closely. Naturally you can leave the DCP open on the ‘Syslog’ tab and new events would just pop up when they are logged. That might not be as convenient as it sounds especially if you are building a network-facing application and are constantly testing and working with the JNIOR using various browsers. Perhaps you are rebooting the unit causing the DCP to reconnect far too often. More typically we periodically make a Command Line connection through Telnet and manually list the log. Here we make use of the CAT command.

mqtt-test /> help cat
CAT filespec

Options:
 -H             Dump file in hex
 -J             Formats JSON
 -P             Displays last page

Displays the contents of a file.
Aliases: CAT, TYPE

mqtt-test /> cat -p jniorsys.log

Now the jniorsys.log file is limited to about 64KB characters. That can represent a lot of lines. Do you really want to list those every time? Here we see that the CAT command also provides the -P option which will show only the last page (25 lines) of the file. Of course you do have to remember to include the option. One side note here is that with JANOS you can supply the options anywhere on the line. So if you at first forget to include the -P you can place it after the filename. No problem.

We can improve on this by making use of JANOS batch file capabilities. A batch file is a kind of script file that can contain commands to be executed one after another. Most operating systems, JANOS included, provide some facility for batch execution. But you might be wondering how do you create batch files or if you do that externally how do you get them onto the JNIOR? Well here’s a tip: You can create them on the fly. Of course, the simpler the file the easier that can be accomplished.

For example we will create a simple batch file called log.bat as as kind of short hand that we can use when we want to display the System Log. Here we simply ECHO the command routing the text to the file. Immediately we can use the short batch file name to execute the command.

mqtt-test /> echo cat -p jniorsys.log > log.bat

mqtt-test /> log
cat -p jniorsys.log
10/03/18 18:54:15.850, FTP/10.0.0.27:58531 uploaded /flash/MQTT.jar [325.8 kbps]
10/03/18 18:54:24.571, ... (etc.)

Here we see that we used the ‘>’ pipe character to route the output to the specified file. If you need to build a batch file with more than one command you can append to it using ‘>>’ as well. The power here comes in combining commands to achieve some goal. The advantage being that you can repeat the procedure easily using the batch file name as shorthand. While batch files in JANOS are not as fully featured as you will find in Linux or MS-DOS systems most of the basics are there.

Suppose instead we want to list only today’s events. Here we create our batch file in way that lists only those entries with today’s date. Check it out.

mqtt-test /> echo grep %DATE% jniorsys.log > log.bat

mqtt-test /> log
grep 10/04/18 jniorsys.log
10/04/18 12:10:48.657, Ending session Command/10.0.0.27:64514 (pid 132)
10/04/18 12:37:53.642, Command/10.0.0.27:64075 login 'jnior' (pid 405)
10/04/18 12:38:05.179, FTP/10.0.0.27:64118 login 'jnior'
10/04/18 12:38:05.711 ... (etc.)

And there you go. You now have a simple way to check recent System Log activity. Now I bet that you are thinking how you might alter this to be even more helpful. Well, if you find that you cannot achieve what you have in mind just let us know. An advantage that you have with INTEG is a direct link to the technical team and the advantage we have is the power to implement what you need.