How do you update and maintain your shell scripts over time?

To use a consistence style is very important set up coding standard and to follow it by code review before put it to production.

In my experience, the key to maintaining effective shell scripts over time lies in adopting a proactive approach to documentation and automated testing. Establishing clear standards from the start and adhering to them has minimized errors and maximized efficiency across multiple projects.

In my opinion metadata plays important role to keep your script up to date. One should always add version at top so if anybody has his copy can compare it to the latest version of script just by looking at the version number of file uploaded to shared repository.

To maintain standards it should be first published and check by code review every time when changes were made. The same process should apply to documentation as well.

This is true. Once I had a pipeline which had duplication code for authenticating Kubernetes credentials. For each step there was code duplications. What I did was encapsulated it in a single script as a module and included it in following scripts. With a single option to choose which Kubernetes environment to select. And this made the code base readability easier.

Good practice to follow standards for structure programming which required length of module not bigger than one page. It make shell script easier troubleshooting and debug.

In my experience, using trap to catch errors is a very valuable tool and key to sustainable scripts. It gives a framework for logging critical failures and an insight into troubleshooting the problem. Logging the information available provides footprints that can help diagnose if it’s a script design flaw or system failure. By adding this into my scripts, the root cause analysis is much quicker, thereby paving the way to a quicker solution and understanding how to mitigate the failure. It’s much easier to automate scripts with robust error handling.

In my time, i've come to love versioning. Although its highly recommended to keep a copy of a repository somewhere else, i'll simply start an empty git-repo on a single folder, to keep track of my changes, substituting the old .bak-version method. Shell-scripts can be hard to develop, maintain and test due to their nature, which is why an integration-test (or test-system) is a benefit. Not only now, but also in 3 years.

Shell scripts are great until they are not. If you find yourself trying to invent classes, modules systems, and complex data structures in a shell script, it probably shouldn't be a shell script anymore. Consider rewriting some or all of it in Python. An interpreter is likely already present, and even older systems have a plethora of standard library modules like argparse, pwd, shlex, subprocess, signal, and so on, so shell scripters will feel right at home. If your application is written in shell, Python, or a hybrid, you can still package it for distribution with pip, making it much easier to load onto new systems and share with others.

On each run of the script internal validations should proof the effective user identity running the script to ensure the use uid/euid is appropriate. Validate presence and permissions of any required resources such as files or directories part of or external to the script. When parsing input: validate that the options and data passed in do not contain escape characters, are of the correct data type, and within expected value range. If the data passed in refers to other files or directories: validate presence and permissions. For statically set values consider using a configuration file to avoid having to change the script directly. Monitor the script and config files for change and alert on detected changes.