How do you shell expand your variables and why?

zephyr@lemmy.world to Programming@programming.dev – 63 points –
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@zephyr echo "${HOME}/docs"

This is the best way. It's also the way the Shellcheck wants sometimes recommends.

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This has never stuck with me, and I hadn't thought about why until now. I have two reasons why I will always write ${x}_$y.z instead of ${x}_${y}.z:

  • Syntax highlighting and shellcheck have always caught the cases I need to add braces to prevent $x_ being expanded as ${x_}.
  • I write a lot of Zsh. In Zsh, braces are optional in way more cases. "$#array[3]" actually prints the length of the third item in array, rather than (Bash:) the number of positional parameters, then the string 'array[3]'.

@gamma I just use them out of consistency and principle, so I don't need to think in which case it is required or not.

I will always write ${x}_$y.z instead of ${x}_${y}.z:

The difference between the two seems different to what's in the OP. Is there a typo here?

in the OP

My reply is to a commenter who said they prefer "${HOME}/docs" over both options in the original image ("$HOME/docs" or "$HOME"/docs). Many people prefer to always include braces around the parameter name out of consistency, instead of only when they are required.

My comment explained why my habit is to only include braces when they are necessary.

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