Commands & Shells Archives - Igor Oseledko

GPT Prompt Engineering

Igor — Mon, 20 Jul 2026 17:34:22 +0000

Originally published July 21, 2023 @ 12:24 pmPicture a giant maze. In the end – a particular piece of cheese (there are many, but this one is special) representing the answer you seek. ChatGPT is the rat traversing the maze. You can help the rat by blocking off the dead-end paths obvious to you. And […]

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Identifying JAR Version Requirements

Igor — Sun, 19 Jul 2026 15:36:27 +0000

Originally published July 20, 2023 @ 9:51 amRecently, I had to upgrade an old Java application running on an equally old Sun Solaris 11 server. Several upgrade candidates arrived as JAR files without much detail about the system requirements. For reasons outside this discussion, upgrading the Java version on the server was out of the […]

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Bash Scripts and MySQL

Igor — Thu, 25 Jun 2026 12:59:12 +0000

Originally published June 26, 2020 @ 12:24 amI frequently use MySQL to store data collected or processed by various shell scripts. The database comes in handy when massaging data with good old awk and sed gets too cumbersome. This is really very basic stuff: just loading some data into MySQL and retrieving it. The usual […]

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Bulk Create Linux Users using Salt

Igor — Thu, 18 Jun 2026 22:16:05 +0000

Originally published June 19, 2020 @ 1:23 pmRecently I ran into a situation where hundreds of VMs recently built via OpenShift/Ansible automation were missing an important local user account used for security audits. While our automation guys were working on tracking down and fixing the build configuration, I needed to add the account manually. Luckily […]

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Randomizing Filenames

Igor — Wed, 29 Apr 2026 17:50:42 +0000

Originally published April 30, 2023 @ 12:15 pmI had a bunch of folders with some old photos, and I needed to randomize the filenames as an easy way to get a random selection of files. This should’ve been easy, but I made the mistake of googling the answer instead of writing this one-liner myself because […]

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Finding Gaps in Timestamps

Igor — Fri, 24 Apr 2026 13:57:47 +0000

Originally published April 25, 2023 @ 8:29 amSometimes knowing when something didn’t happen can be just as valuable as knowing when it did. For reasons yet to be determined, my Salt Master server needs to be bounced occasionally. Not the whole server – just the salt-master service. I needed to find a good time to […]

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Coronavirus Stats in Bash

Igor — Thu, 19 Mar 2026 08:00:48 +0000

Originally published March 19, 2020 @ 10:37 pmThe result of my morbid fascination with the coronavirus situation is this quick bash script that parses Johns Hopkins University coronavirus data to generate a quick report for the current date for the specified countries. The plan is to add some statistical analysis to spot potential anomalies in […]

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Updating Lynis

Igor — Sat, 28 Feb 2026 02:22:08 +0000

Originally published February 29, 2020 @ 5:04 pmLynis is an excellent security audit tool for Linux and various Unix derivatives. I have a small wrapper script that runs Lynis via a cron job, does a selective diff with the previous run’s output, and sends me an email. Unfortunately, Lynis does not update itself automatically and […]

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Converting Geofency Data to Google Maps

Igor — Sat, 07 Feb 2026 17:25:10 +0000

Originally published February 8, 2023 @ 8:57 amGeofency is a time and location tracking app for iOS. I’ve been using it for many years to keep track of my whereabouts. At times, this information can come in quite handy. The app does not track your movements continuously. Instead, it uses Geofencing and iBeacon technology, which […]

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Reading Multi-Line Input in One Loop Iteration

Igor — Sat, 31 Jan 2026 23:45:24 +0000

Originally published February 1, 2023 @ 2:43 pmBash loops can read the input as words or lines, but what if you needed to accept multi-line input with a single loop iteration? In the following simple example, we randomly select a hundred lines from /var/log/messages and count the number of characters in each line: shuf -n […]

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