After writing more and more bash scripts for a client, I’ve decided to write down my thoughts about it. This assumes you have some knowledge about bash, as it is not intended as a beginner’s tutorial. Why bash scripts? Bash is present in almost every unix/linux-based stack, now some Windows as well. An exception is the ‘alpine’ docker images, which have a smaller, lighter shell (more on that later) Everything that you can automate, you can do from bash.

Context For a client, we have worked on a service that works with files (containing sensitive data) that get corrupted very often. The use case is generally: Two/Three file opens per day One modification per 10 file opens One corruption per 100 file opens Initial solution The initial solution was just to copy the file (file.txt) before opening, after closing. This results in two files (YYY-MM-DDTHH-mm-ss_before_file.txt, YYY-MM-DDTHH-mm-ss_after_file.txt). As this solution quickly became unmaintainable, the client developed a solution to hash the contents of the file and to remove the duplicated files.

As the preface for the guide for on-call support, a positive note: README You’re cool. I know it. Do not trust yourself, trust me that I trust you. You might be sleepy. It’s OK Everything is going to be fine. Take 5 minutes to think about anything, anytime. Especially before any rash decision. With great power comes great responsibility. Use it wisely. Restoring the services comes first, investigation comes second Do the very minimum of investigation after the incident (collect things that might disappear), leave the rest for the next day on office hours Whenever everything is done, go to sleep but keep an eye on your phone.

With my pairing mate we have refactored this piece of functional code. Original code: function filterTokens (rawTokens) { const cleanedTokens = rawTokens.map(token => (token.length && token[0] === '-') ? token.substring(1) : token) return cleanedTokens.filter(token => token !== '' && stopWordsArray.indexOf(token) === -1) } Refactored code: function filterTokens (rawTokens) { const cleanedTokens = rawTokens.map(token => startsWithADash(token) ? removeDashFrom(token) : token) const processedTokens = cleanedTokens.filter(token => isNotEmpty(token) && isNotAStopWord(token)) return processedTokens function startsWithADash (token) { return (token.

Quoting the book, Why is programming fun? What delights may its practitioner expect as his reward? First is the sheer joy of making things. As the child delights in his mud pie, so the adult enjoys building things, especially things of his own design […] Second is the pleasure of making things that are useful to other people. Deep within, we want other to use our work and to find it helpful.