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Shell script best practices, from a decade of scripting things

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Re: Shell script best practices, from a decade of scripting things

#21

Post by [deleted] »

grumbel wrote: post #18

What would be the justification for 'cd "$(dirname "$0")"'? Going to the scripts directory does not seem very helpful. If I don't care about the current directory, I might just go to '/' or a temporary directory, when I do care about it I better stay in it or interpreting relative command line arguments is going to get difficult. When symbolic links are involved, dirname will also give the wrong directory.

[deleted]

Re: Shell script best practices, from a decade of scripting things

#22

Post by IshKebab »

midasuni wrote: post #8
Emigre_ wrote: post #4

These could be linting rules for bash script files.

If you need to follow these rules your script probably shouldn’t be written as a shell script.

Ha yeah someone should make a single lint "Your script is over 100 lines. You should rewrite it in a sane language!"

Re: Shell script best practices, from a decade of scripting things

#23

Post by Beltalowda »

jph wrote: post #15

I favor POSIX and dash over bash, because POSIX is more portable. If a shell script needs any kind of functionality beyond POSIX, then that's a good time to upgrade to a higher-structure programming language. Here's my related list of shell script tactics: http://github.com/sixarm/unix-shell-script-tactics

I've rewritten a lot of shell scripts with awk. Obviously it's not a good fit for everything, but when it is a good fit I found it a very pleasant experience. In spite of using Unix systems for 20 years I only learned awk a few years ago and I really beat myself up for not learning it earlier.

Re: Shell script best practices, from a decade of scripting things

#24

Post by tonnydourado »

I would add a "zero" best practice: don't. If you're thinking about writing enough shell script that it is worth putting it in a file, consider other languages or tools.

I'm not saying *never* write shell scripts, but always consider doing something else, or at least add a TODO, or issue, to write in a more robust language.

Re: Shell script best practices, from a decade of scripting things

#25

Post by rockyj »

Speaking of shell, which language do you think has the best interoperatibility with shell commands. I mean, running a command, parsing the output, looping, adding user interaction etc. with the least amount of friction. Ruby used to come close for me, just put the command in backticks `` and write the main logic in Ruby, but I want to hear if there is something better.

Re: Shell script best practices, from a decade of scripting things

#26

Post by Beltalowda »

shiomiru wrote: post #5
emptyparadise wrote: post #2

Personally I try to stick with POSIX sh (testing with dash), if I need anything fancier, I reach for Perl or Python.

POSIX sh also yields better performance, provided you're using dash.

I ran some tests some time ago, and the differences are pretty minimal unless you start doing comp-sci-y stuff in shell scripts. But for the type of thing that people typically use shell scripts for: it makes basically no meaningful difference.

Re: Shell script best practices, from a decade of scripting things

#28

Post by stevekemp »

rockyj wrote: post #25

Speaking of shell, which language do you think has the best interoperatibility with shell commands. I mean, running a command, parsing the output, looping, adding user interaction etc. with the least amount of friction. Ruby used to come close for me, just put the command in backticks `` and write the main logic in Ruby, but I want to hear if there is something better.

I did that for 10+ years with perl, but I guess that these days Ruby and Python would be equally valid choices.

To be honest these days I use shell scripts, and if they get too large I'll replace with either golang or python. I don't love python, especially when dependencies are required, but it is portable and has a lot of things built-in that mean executing "standard binaries" isnt required so often.

Re: Shell script best practices, from a decade of scripting things

#29

Post by Beltalowda »

grumbel wrote: post #18

What would be the justification for 'cd "$(dirname "$0")"'? Going to the scripts directory does not seem very helpful. If I don't care about the current directory, I might just go to '/' or a temporary directory, when I do care about it I better stay in it or interpreting relative command line arguments is going to get difficult. When symbolic links are involved, dirname will also give the wrong directory.

It's sometimes a bit convenient if you want to read file from the directory the script is stored in. Overall I found it more confusing and awkward than anything else, and prefer setting it explicitly. It's still okay for a quick script though, but as general "best practices" advice: meh.

Re: Shell script best practices, from a decade of scripting things

#30

Post by laserbeam »

grumbel wrote: post #18

What would be the justification for 'cd "$(dirname "$0")"'? Going to the scripts directory does not seem very helpful. If I don't care about the current directory, I might just go to '/' or a temporary directory, when I do care about it I better stay in it or interpreting relative command line arguments is going to get difficult. When symbolic links are involved, dirname will also give the wrong directory.

To be fair, it's common to want to be in the script directory for certain classes of scripts. For example, scripts which automate some tasks in a project, and are written for a project.

But, more importantly, people will google for how to set cwd to the script directory more often then will google how to go to an absolute path. Having 'cd "$(dirname "$0")"' as reference in an article discussing best practices and the topic of changing the directory early, is a good idea.

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