Linux articles with focus on shell scripting and monitoring. Here you will find longer texts about solving real world problems with code examples.
I once had a need to monitor the origin of HTTP requests, track it in real time from web server log. Since this need was actually nothing more but pure curiosity, I was not willing to pay for it. So I started looking for free solutions for this purpose – convert IP to country. Here is what it all ended at…
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You may want to read log files for newly appended data. You could do it by knowing how many lines you read before and how many lines you have “now”. But when you have large log files, this approach will become very slow. Try to run “wc -l” on file which has tens of millions of lines and you’ll see how slowly it counts. And you would have to do something like that each time you are reading new portion of data. What to do? Read log in bytes instead. Here is how.
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If you have a need to detect corrupted images, you can easily do it with command line utility “identify“.
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Sometimes you may encounter situations, when you wish to display all possible combinations of characters from given charset (e.g. some brute-force task). For example, print “a … zzz”, i.e. range is “a … z” and maximum length is 3. You can easily do this in bash (print recursively).
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Let’s suppose that you have just opened Linux terminal for the first time in your life. Your wish is to write nothing but bash “hello world” type of thing. As this command is one-liner, you can simply do this:
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