General Advice for shell scripts

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#!/usr/bin/env bash

  

A folder dotfiles as git repository and a dotfiles/install that soft links all configurations into their places.

Two files, ~/.zshrc (without secrets, could be shared) and another for secrets (sourced by .zshrc if exist secrets).

Use shellcheck

Do you use bash?

Personally I use Bash for scripting. It strikes the balance of being available on almost any system, while also being a bit more featureful than POSIX. For interactive use I bounce between bash and zsh depending on which machine I'm on.

Do you write #!/bin/bash or #!/bin/sh?

I start my shell scripts with #! /usr/bin/env bash. This is the best way of ensuring that the same bash interpreter is called that the user expects (even if more than one is present or if it is in an unusual location)

Do you have two folders, one for proven commands and one for experimental?

By commands, do you mean bash scripts? If so, I put the ones I have made relatively bulletproof in ~/bin/, as bash usually makes them automatically on the path with this particular folder name. If I'm working on a script and I don't think it's ready for that, or if it goes with a specific project/workflow, I will move it there.

Do you sync the folder between your server and your workstation?

No. I work on lots of servers, so for me it's far more important to know the vanilla commands and tools rather than expect my home-made stuff to follow me everywhere.

good practice? general advice?

Pick a bash style guide and follow it. If a line is longer than 80 characters, find a better way of writing that logic. If your script file is longer than 200 lines, switch to a proper programming language like Python. Unless a variable is meant to interact with something outside of your script, don't name it an all caps name.

is it bad practice to create a handful of commands like podup and poddown that replace podman compose up -d and podman compose down or podlog as podman logs -f --tail 20 $1 or podenter for podman exec -it "$1" /bin/sh?

This is a job for bash aliases.

I use bash for scripts almost exclusively even though i use zsh interactively (startup scripts for zsh are an obvious exception).

The vast majority of my scripts start with

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  set -e -u


  

which makes the script exit if a command (that is not in a few special places like an if) exits with an error status code and also complains about unbound variables when you use them.

Use

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bash -n


  

and

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shellcheck


  

to test your script for errors and problems if you try it.

Always use curly braces for variables to avoid issues with strings after the variable name being interpreted as part of the variable name.

Always use 10# before numbers in $(()) expressions to avoid leading zeroes turning your decimal number variables into octal ones.

Always use

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while read -r foo
do
...
done < <(command ...)

  

instead of

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command ... | while read -r foo
do
...
done


  

to avoid creating a subshell where some changes you make will not affect your script outside the loop.

In

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while read -r foo
do
...
done < ...


  

loops always make sure you redirect all stdin from /dev/null or otherwise close it with suitable parameters or the content of your loop will eat some of the lines you meant for the read. Alternatively fill a bash array in the loop and then use a for loop to call your commands and do more complex logic.

When using temporary directories or similar resources use

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cleanup()
{
 ...
}
trap cleanup EXIT


  

handlers to clean up after the script in case it dies or is killed (by SIGTERM or SIGINT,...; obviously not SIGKILL).

When writing scripts for cronjobs take into account that the environment (PATH In particular) might be more limited. Also take into account that stderr output and non-zero exit status can lead to an email about the cronjob.

Use pushd and popd instead of cd (especially cd ..), redirect their output to /dev/null. This will prevent your scripts from accidentally running later parts of the script in a wrong directory.

There are probably many other things to consider but that is just standard stuff off the top of my head.

If you do need any sort of data structure and in particular arrays of data structures use a proper programming language. I would recommend Rust since a compiled language is much easier to run on a variety of systems than the Python so many others here recommend, especially if you need to support the oldest supported version of an OS and the newest one at the same time.

Use

set -x

For debugging

That's the way I do it:

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#!/usr/bin/env nix
#! nix shell nixpkgs#nushell <optionally more dependencies>  --command nu

<script content>

  

But those scripts are only used by me

Several things

• write bash and nothing else (except posix sh)
• find a good way to take notes. It shouldn't be in your bashrc
• only write fish for fish config
• use $!/usr/bin/env bash

Shell scripts are one of the things that makes Linux what it is. They're relatively easy to create, powerful, etc. It was the thing that drove me to it from Windows in the first place.

One thing I would recommend against is creating dozens of utility scripts and/or aliases for things you run frequently. I have found it's much better in the long-run to simply learn the "proper" commands and switches. If you use them often enough you start to type them very quickly. When you create helpers you start to learn your own ecosystem and will be lost on any system that doesn't have your suite of helper apps installed.

There are exceptions to this to be sure (e.g. I always alias 'l=ls -FhlA') but I would specifically avoid the podup and poddown ones myself. I've gotten very quick at typing "docker run -it --rm foo" just by rote repetition.

You're free to do as you like though. Maybe you'll only run Linux on your own desktop so that's all that matters. But something to keep in mind. I would at least learn the commands very well first and then later alias or script them for convenience.

• I use bash, because I never had the time to learn anything else.
• Like @jlsalvador@lemmy.ml said, I use the #!/usr/bin/env bash shebang.
• Nope
• Also nope
• Nope. Shell scripts reside in Git repos on Gitlab/Gitea/Forgejo and are checked out using Ansible playbooks onto the servers as necessary.
• For scripts? Python. Read this blog post by the great @isotopp@chaos.social. For interactive use? bash is just fine for me, though I've customized it using Starship and created some aliases to have colored/pretty output where possible.
• Use shellcheck before running your scripts in production, err on the side of caution, set -o pipefail. There are best practices guides for Bash, use those and you'll probably be fine.
• Be prepared to shave yaks. Take breaks, touch grass, pet a dog. Use set -x inside your Bash script or bash -x scriptname on the CLI for debugging. Remember that you can always fallback to interactive CLI to test/prepare commands before you put them into your script. Think before you type. Test. Optimize only what needs optimization. Use long options for readability. And remember: Always code as if the guy who ends up maintaining your code will be a violent psychopath who knows your address.
• Nope, it's absolutely not bad practice to create aliases to save you some typing in interactive shell. You shouldn't use them inside your scripts though, because they might/will not be available in other environments.

I switched to fish because it has tab completion Yeah, so does Bash, just install it.

Oh, I also "curate" a list of Linux tools that I like, that are more modern alternatives to "traditional" Linux tools or that provide information I would otherwise not easily get. I'll post i

___

I use Bash for scripts, though my interactive shell is Fish.

Usually I use #!/usr/bin/env bash as shebang. This has the advantage of searching your PATH for Bash instead of hardcoding it.

My folders are only differentiated by those in my PATH and those not.

Most of my scripts can be found here. They are purely desktop use, no syncing to any servers. Most would be useless there.

For good practice, I'd recommend using set -euo pipefail to make Bash slightly less insane and use shellcheck to check for issues.
This is personal preference, but you could avoid Bashisms like [[ and stick to POSIX sh. (Use #!/usr/bin/env sh then.)

With shortened commands the risk is that you might forget how the full command works. How reliant you want to be on those commands being present is up to you. I wouldn't implement them as scripts though, just simple aliases instead.
Scripts only make sense if you want to do something slightly more complex over multiple lines for readability.

You are way over thinking it.

• I usually use bash/python/perl if I can be sure that it will be available on all systems I intend to run the scripts. A notable exception for this would be alpine based containers, there it's nearly exclusively #!/bin/sh.
• Depending on the complexity I will either have a git repository for all random scripts I need and not test them, or a single repo per script with Integrationtests.
• Depends, if they are specific to my setup, no, otherwise the git repository is public on my git server.
• Usually no, because the servers are not always under my direct control, so the scripts that are on servers are specific to that server/the server fleet.
• Regarding your last question in the list: You do you, I personally don't, partly because of my previous point. A lot of servers are "cattle" provisioned and destroyed on a whim. I would have to sync those modifications to all machines to effectively use them, which is not always possible. So I also don't do this on any personal devices, because I don't want to build muscle memory that doesn't apply everywhere.

I primarily operate in strict standard compliance mode where I write against the shell specifications in the lastest Single Unix Specification and do not use a she-bang line since including one results in unspecified, implementation-defined behavior. Generally people seem to find this weird and annoying.

Sometimes I embrace using bash as a scripting language, and use one of the env-based she-bangs. In that case, I go whole-hog on bashisns. While I use zsh as my interactive shell, even I'm not mad enough to try to use it for scripts that need to run in more than one context (like other personal accounts/machines, even).

In ALL cases, use shellcheck and at least understand the diagnostics reported, even if you opt not to fix them. (I generally modify the script until I get a clean shellcheck run, but that can be quite involved... lists of files are pretty hard to deal with safely, actually.)

Am I missing something - doesn't bash have tab completion or of the box?

• Fish. Much, much saner defaults.
• I am writing #!/usr/bin/env sh for dead simple scripts, so they will be a tiny bit more portable and run a tiny bit faster. The lack of arrays causes too much pain in longer scripts. I would love to use Fish, but it lacks a strict mode.
• No, why would I?
• I used to share all my dotfiles, scripts included, but I was too afraid that I would publish some secrets someday, so I stopped doing that. For synchronizing commands, aliases and other stuff between computers I use Chezmoi.
• To use Fish instead of fighting with start up time of Zsh with hundreds of plugins
• Always use the so-called "strict mode" in Bash, that is, the set -euo pipefail line. It will make Bash error on non-zero exit code, undefined variables and non-zero exit codes in commands in pipe. Also, always use shellcheck. It's extremely easy to make a mistake in Bash. If you want to check the single command exit code manually, just wrap it in set +e and set -e.
• Consider writing your scripts in Python. Like Bash, it also has some warts, but is multiplatform and easy to read. I have a snippet which contains some boilerplate like a main function definition with ArgumentParser instantiated. Then at the end of the script the main function is called wrapped in try … except KeyboardInterrupt: exit(130) which should be a default behavior.
• Absolutely not a bad practice. If you need to use them on a remote server and can't remember what they stand for, you can always execute type some_command. Oh, and read about abbreviations in Fish. It always expands the abbreviation, so you see what you execute.

I use sh to attempt to keep it compatible with POSIX systems.

I use pain bash. Never really tried zsh and fish, since most of my Linux work is on servers and I don't really care for extra features.

I try and write idempotent scripts when possible.

I wouldn't create those aliases on a fleet because writing them to the configuration file of your shell in an idempotent fashion is hacky and my VMs are like cattle.

Yes, using bash on all boxen.

Scripts start with #!/bin/sh ,because, that gives quicker execution times.

Any simple aliases, I put in .bash_aliases

Tried tcsh and zsh around 30yrs ago, all bash since then.

I use bash as my interactive shell. When ~20 years ago or so I encountered "smart" tab completion for the first time, I immediately disabled that and went back to dumb completion, because it caused multi-second freezes when it needed to load stuff from disk. I also saw it refuse to complete filenames because they had the wrong suffix. Maybe I should try to enable that again, see if it works any better now. It probably does go faster now with the SSDs.

I tried OpenBSD at some point, and it came with some version of ksh. Seems about equivalent to bash, but I had to modify some of my .bashrc so it would work on ksh. I would just stick to the default shell, whatever it is, it's fine.

I try to stick to POSIX shell for scripts. I find that I don't need bashisms very often, and I've used systems without bash on them. Most bash-only syntax has an equivalent that will work on POSIX sh. I do use bash if I really need some bash feature (I recently wanted to set -o pipefail, which dash cannot do apparently, and the workaround is really annoying).

Do not use #!/bin/sh if you're writing bash-only scripts. This will break on Debian, Ubuntu, BSD, busybox etc. because /bin/sh is not bash on those systems.

Do you use bash? Yes because it is everywhere and available by default.

Do you use bash? If not, which one do you use? zsh, fish? Why do you do it?

Mostly fish, because it just feels much more modern than bash, it has good built-in autocomplete and I don't have to install millions of plugins like of zsh.

Do you write #!/bin/bash or #!/bin/sh? Do you write fish exclusive scripts?

#!/usr/bin/env bash Occasionally I also write fish scripts. Just replace sh with fish.

What should’ve people told you what to do/ use?

zoxide

general advice?

As @crispy_kilt@feddit.de already suggested, use shellcheck.

is it bad practice to create a handful of commands like podup and poddown that replace podman compose up -d and podman compose down or podlog as podman logs -f --tail 20 $1 or podenter for podman exec -it "$1" /bin/sh?

I don't think so

Yes fish is great. It has some special syntax for functions, I will add my configs soo.

set fish_greeting is useful to silence it.

User scripts can go to ~/.local/bin which is already in the path.

You can split up your shell configs into topics, and put them into ~/.config/fish/conf.d/abc.conf

I recommend writing everything in Bourne shell (/bin/sh) for a few reasons:

• Bash is more capable, which is nice, but if you're fiddling with complex data structures, you probably should be using a more maintainable language like Python.
• Bash is in most places, but crucially not everywhere. Docker-based deployments for example often use Ash which is very similar to Bash, but lacks support for arrays and a few other things.
• Bourne's limitations force you to rethink your choices regularly. If you find yourself hacking around a lack of associative arrays for example, it's probably time to switch to a proper language.

Also two bits of advice.

1. Use shellcheck. There's a website that'll check your script for you as well as a bunch of editor extensions that'll do it in real time. You will absolutely write better, safer code with it.
2. If your script exceeds 300 lines. Stop and rewrite it in a proper language. Your future self will thank you.

A good idea i have been spreading around relevant people lately is to use ShellCheck as you code in Bash, integrate it in your workflow, editor or IDE as relevant to you (there's a commandline tool as well as being available for editors in various forms), and pass your scripts through it, trying to get the warnings to go away. That should fix many obvious errors and clean up your code a bit.

Bash script for simple things (although Fish is my regular shell) and Node or Python scripts for complex things. Using #!/usr/bin/env node works just like it would for Bash so you know.

I use fish shell only now. Used to only write bash, but I've started writing some fish scripts. I wouldn't try to plan too much WRT shell scripting up front. Just fix your pain points as you go.

• Do you use bash? If not, which one do you use? zsh, fish? Why do you do it?
• Do you write #!/bin/bash or #!/bin/sh? Do you write fish exclusive scripts?

I use bash, and I use #!/bin/bash for my scripts. Some are POSIX compliant, some have bashisms. But I really don't care about bashisms, since I explicitly set the bash as interpreter. So no, no fish exclusive scripts, but some "bash exclusive" scripts. Since fish is aimed towards being used as interactive shell I don't see a real reason to use it as interpreter for scripts anyways.

• Do you have two folders, one for proven commands and one for experimental?
• Do you publish/ share those commands?
• Do you sync the folder between your server and your workstation?

I have my scripts in $HOME/.scripts and softlink them from a directory in $PATH. Some of the scripts are versioned using Git, but the repository is private and I do not plan sharing them because the repoand the scripts scripts contain some not-tho-share information and mostly are simply not useful outside my carefully crafted and specific environment. If I want to share a script, I do it individually or make a proper public Git repository for it.

Since my server(s) and my workstations have different use cases I do not share any configuration between them. I share some configuration between different workstations, though. My dotfiles repository is mainly there for me to keep track of changes in my dotfiles.

is it bad practice to create a handful of commands

It becomes bad practice if it is against your personal or corporate guidelines regarding best practices. While it is not particularly bad or insecure, etc. to create bash scripts containing a single command, maybe use an alias instead. The $1 is automatically the first parameter after typing the alias in the shell.

 bash

    
alias podup="podman compose up -d"
alias poddown="podman compose down"
alias podlog="podman logs -f --tail 20"

  

Not quite sure about the podman syntax, if podman exec /bin/sh -it "$1" also works, you can use alias podenter="podman exec /bin/sh -it, Otherwise a simple function would do the trick.

Btw, if you ever wondered why Debian uses dash as /bin/sh (the switch was a bit annoying at the time), I think the reasoning was something like this:

• dash is a bit faster, which might have saved a second or two on boot times (this was before systemd). Same applies to compilation times, configure scripts run faster with dash.
• A bunch of #!/bin/sh scripts in Debian did not actually work if you replaced /bin/sh with another shell, which I guess some people wanted to do. Making dash the default /bin/sh forced everyone to fix their scripts.

Also some history on the abomination that is m4sh, famously used by GNU autoconf configure.ac scripts. Apparently when autoconf was released in 1991, there were still some Unix systems that shipped some 70s shells as the default /bin/sh. These shells do not support shell functions, which makes creating any sort of shell programming library pretty much impossible (I guess you could make a folder full of scripts instead of functions). They decided to use m4 preprocessor macros instead, as a sort of poor man's replacement for functions.

In hindsight, it wish they had told commercial Unix sysadmins to install a proper /bin/sh or gtfo. But the GNU people thought it was important to make it as easy as possible to install free software even on commercial Unices.

I use bash and I usually put /bin/bash in my scrtipts, because that's where I know it works. /bin/sh is only if it works on many/all shells.

I don't have many such scripts, so I just have one. I don't really share them, as they are made for my usecase. If I do create something that I think will help others, then yes, I share them in git somewhere.

I do have a scripts folder in my Nextcloud that I sync around with useful scripts.

Some of your examples can probably just be made into aliases with alias alias_name="command_to_run".

I make my scripts with modern shells in mind since they let you use arrays for arguments which is vastly superior to doing \ for continuing the script line, I give the example here https://docs.blissos.org/installation/install-in-a-virtual-machine/advanced-qemu-config/#flexible-bash-scripting