61–70 of 195 posts
I think Python is getting so popular & ubiquitous now I can't see any reason to write bash scripts any more except for perhaps very simple ones that are just a few lines. Other people's bash scripts are regularly just too difficult and complex to maintain.
Many people who write scripts do not factor the environment they are run in and miss including traps to handle events like being terminated mid-way thru and cleaning up to a sanitized state. After all, creating a file, you can't presume their is enough free space, but people do in scripts all the time. Then you have scripts that you want run once and if run again not have any more effect. FOr example a script to be r…
I have not been doing DevOps for very long, but a useful trick I've found is to create a staging directory, perform my work there, diff the result with the existing state, and copy if a difference exists. I've found it very easy to clean up to a sanitized state in this way; the existing state is safe, since all I have to do is just destroy my work.
Another approach is to create a unique directory (named by hash or date) with the results, and once it's good, symlink the real directory to it. (Full disclosure, I stole this approach from nextflow.io, a great workflow system aimed at bioinformatics).
ln -sfn "build-cache/2019-07-07-21:23:04" "build"Earlier quoted context omitted.
I have not been doing DevOps for very long, but a useful trick I've found is to create a staging directory, perform my work there, diff the result with the existing state, and copy if a difference exists. I've found it very easy to clean up to a sanitized state in this way; the existing state is safe, since all I have to do is just destroy my work.
What do you use to compute the diff? Just the diff command itself on individual files?
Many people who write scripts do not factor the environment they are run in and miss including traps to handle events like being terminated mid-way thru and cleaning up to a sanitized state. After all, creating a file, you can't presume their is enough free space, but people do in scripts all the time. Then you have scripts that you want run once and if run again not have any more effect. FOr example a script to be r…
The first example ("idiom") is bit tricky, because the title is "Creating an empty file". An alternative would for example be echo -n > example.txt Both fit the description of "Creating an empty file". Is it idempotent, or more or less so than `touch example.txt`? If there is already an existing file, then touching it obviously will not empty it, so the end state is not "empty file exists" like one would expect from…
If a file has a line ending in it, is it truly empty?
A good way to remember idempotent is to think of the 'delete' or 'mark as read' function for gmail. You can delete an email or mark it as read even if it's been done before (on another open screen as an example).
Terminology is broken. Correct is "ln -s TARGET LINK_NAME" per its man page.
I think Python is getting so popular & ubiquitous now I can't see any reason to write bash scripts any more except for perhaps very simple ones that are just a few lines. Other people's bash scripts are regularly just too difficult and complex to maintain.
Of course, others would prefer, say, Clojure, or Kotlin (although the JVM startup time is the worst of all), but therein lies the issue... We're stuck with Bash scripting because everyone (more or less) knows/understands it to some extent, it's installed everywhere, and it has essentially no startup-time cost.
Great article, but a common scenario is missing: I want to run a long running script, but not if another copy of it is already running.
https://linux.die.net/man/1/flock would probably help
Let's try to avoid using a hammer on anything that resembles a nail: https://github.com/valvesoftware/steam-for-linux/issues/3671
How is that related to the article aside from "both involve bash"?