Category Archives: shell

Testing Alertmanager

Posted on September 13, 2020 by Matthias

When a Prometheus alerting rule fires, the Prometheus server sends a notification to the Alertmanager, which is then responsible for processing that alert further, i.e. by routing it to an appropriate alerting channel (e-mail, Slack, …). In order to test … Continue reading →

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A Quick Introduction to sed(1)

Posted on July 29, 2017 by Matthias

The sed(1) stream editor is one of the most powerful tools from the classic Unix tool box. It is a close cousin to the ed(1) command line editor and a descendant of the ex(1) editor, the command line mode of … Continue reading →

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Quick Tip #6: Triggering Actions on File Close

Posted on December 30, 2013 by Matthias

Sometimes it’s useful to trigger an action after a file is closed. Suppose you started a lengthy download on your notebook and you want to suspend it as soon as the download is done. There are several ways to achieve … Continue reading →

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Quick Tip #5: Navigating in Source Trees

Posted on April 14, 2013 by Matthias

I often move around in checked out Subversion or Git source trees on a Bash command line. Directory structures tend to get quite deep (especially in Java projects), so one problem keeps coming up frequently: Changing back to the base … Continue reading →

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Bourne Shell Parameter Expansion

Posted on January 20, 2013 by Matthias

Classic Bourne Shell has a handy feature that many people don’t seem to know: Parameter Expansion. Stephen Bourne describes it in An Introduction to the UNIX Shell, which is part of the original Unix V7 manuals from 1978. Among other … Continue reading →

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Scripts That Just Don’t Work

Posted on July 22, 2012 by Matthias

Sometimes people ask for my help when their shell scripts don’t work. I’ve seen all kinds of problems, ranging from trivial to really, really weird. The one I’m describing in this article is definitely from the weird category, but I’ve … Continue reading →

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Quick Tip #4: Sorting Large Files

Posted on May 23, 2010 by Matthias

With traditional Unix sort(1), the size of the files you can sort is limited by the amount of available main memory. As soon as the file gets larger and your system has to swap, performance degrades significantly. Even GNU sort … Continue reading →

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Quick Tip #2: Set Operations Using Shell Tools

Posted on August 19, 2009 by Matthias

Everybody knows that Unix shell utilities are powerful. Even though they’re text-based, you can build a lot of useful things outside of the text domain. Today I’ll show you how to implement set operations. All we need are sorted files … Continue reading →

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