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Category Archives: shell
Testing Alertmanager
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
A Quick Introduction to sed(1)
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
Quick Tip #6: Triggering Actions on File Close
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
Quick Tip #5: Navigating in Source Trees
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
Bourne Shell Parameter Expansion
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
Scripts That Just Don’t Work
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
Quick Tip #4: Sorting Large Files
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
Quick Tip #2: Set Operations Using Shell Tools
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