× Most sysadmins reach for awk not because they planned to, but because grep stopped being enough. You have a log file, you need to count something, filter by a field, or pull a number out of structured output. That is exactly what awk for log analysis is built for. This guide is for Linux […]
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× You've got three projects to spin up today, and the first thing you do is open /etc/apache2/sites-available/ and start typing another virtual host config from scratch. Again. If you manage Apache on Ubuntu or Debian-based systems and find yourself creating virtual hosts more than once a week, this is for you. After working through […]
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× You open a 200,000-line log file, and your boss asks you to create a report showing how many failed requests were made from each IP address before the end of the day. Most users will use Python. The ones who actually know what they're doing will use awk and get their answers within 45 […]
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× It’s time to stop using grep as your primary debugging and search tool, and it’s time to understand why. You may have already identified the column of interest and located the pattern you need to find. However, when you start combining cut, grep, and sort to extract that information, things can become confusing very […]
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When your deployment script runs at the last minute on a Friday, everything appears fine except that the old database hostname is still present in the configuration file. After a few minutes of searching through files with grep, staring blankly into space, and attempting to run the script again, someone finally asks, "Did you sed […]
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Anyone familiar with Bash scripting has probably needed to replace a configuration file value using sed as part of a pre-deployment process. If your variable (for example, one defined in your script) is not being replaced by sed, you are likely experiencing what is known as the "quoting trap", a problem that nearly every sed […]
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The point where grep really shines is when you are staring at a log file with 40,000 entries and only one error buried somewhere in the middle, and you desperately need to see it on your screen right now. I once dealt with intermittent 500 errors on a production server. I spent hours manually scanning […]
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You wrote a Bash function that returned the value you were trying to see. Then, you started searching through variables, only to find that none of them contained anything. This can happen to anyone. The problem is not with your function (it works exactly as designed) or with Bash itself (it behaves the way it […]
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You are sitting down to write a 300-line deployment script and realize the same 15 lines of disk-space checking code appear in four different places. If you make a change in one location, you now have to go hunting through your entire codebase to see where else those lines of code exist. And if you […]
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I am knee-deep in a production project. I want my script to take 200+ server log files from a directory, read each one individually, and never require me to touch the keyboard while it runs. At that point, Bash loops stop being about tutorials and start becoming practical. I have been there too. My first […]
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You create an executable script that continually retries a failed network or database connection, but it only runs once and exits. In other cases, the condition logic is reversed, causing the loop to continue indefinitely. If either situation sounds familiar, you are in the right place. I once wrote a backup script for a production […]
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The decision to use a bash for loop comes down to how much time you want to spend typing file names. If you've ever found yourself with 200 files all needing the same operation run on them, as I did during a log cleanup task, then using a for loop will save you hours of […]
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Writing a script to calculate disk usage percentages and send an email alert when a threshold is reached might sound straightforward at first. However, after writing half the script, trying something as simple as result=$a/$b can leave you staring at bash wondering what just happened. No error message. No useful output. Just silence. That exact […]
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Most programmers write their first Bash if statement using [ ] (or sometimes [[ ]]), run into a space-in-variable bug, spend an hour searching Google for a fix, and eventually hear about [[ ]] as some kind of magic solution without fully understanding how the two actually differ. I was one of those people. I […]
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You’ve got all of your variables defined, your script appears correct, and then when you run echo '$APP_DIR', the terminal spits back a dollar sign instead of the actual directory path. You are now sitting in front of the terminal wondering, “What just happened?” I wrote echo '$APP_DIR' using single quotes and could not understand […]
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11 Bash Variables and Default Values Made Easy | LinuxTeck Learning bash variables types explained with examples is the foundation every Linux scripter needs before writing anything serious. The first bash script I attempted to run produced an error that made absolutely no sense to me. It turned out I had written name = "LinuxTeck" […]
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