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Which command substitution do you prefer in shell scripts: backquotes `` or $() syntax? (ani.social)
submitted 1 year ago by to c/linux@programming.dev
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Looks like $(...) is better, but I still pretty often see `...` in some articles.

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[–] 18 points 1 year ago* (3 children)

$() for me, to quote from

https://www.shellcheck.net/wiki/SC2006

Backtick command substitution `...` is legacy syntax with several issues.

  1. It has a series of undefined behaviors related to quoting in POSIX.
  2. It imposes a custom escaping mode with surprising results.
  3. It's exceptionally hard to nest.

$(...) command substitution has none of these problems, and is therefore strongly encouraged.

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  • [–] 4 points 1 year ago (2 children)

    Shellcheck is a great tool for scripting.

    When I'm building a new script, I usually add the following function to the script and run the function before anything else. The script will exit immediately if any issues are found so I have a chance to correct things. If no issues are found, the script will simply continue.

    It's small and simple so it's easy to remove when I'm done building a script.

    script_check() {
    if ! shellcheck "${0}"; then
        exit 1
    fi
}

script_check

    Shellcheck has helped me learn a lot about scripting and I strongly recommend using it too.

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    • [–] 16 points 1 year ago

    never backquotes, it's unintuitive

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    [–] 7 points 1 year ago

    Backticks are not very distinct, as they can be confused with single quotes (depending on the font). Also $() shows the beginning and end of the command very clearly. This is even more important when you have multiple of them in some variable in example. Not to mention that you can nest $(), but that is something I personally don't like to do anyway.

    There are some functional differences too: https://www.gnu.org/software/bash/manual/html_node/Command-Substitution.html , such as that backtick command set as an alias in your bashrc will be executed once on load. While $() version is executed every time you execute the alias. Also backslash is literal in the backtick variants (with exception). All in all I never use backtick command substitution; it's confusing, limited and deprecated.

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    [–] 7 points 1 year ago (1 child)

    I'm using fish, so it's ().

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  • [–] 2 points 1 year ago

    I prefer this as well, but just adding that Fish also supports $() for those that don't know.

    I keep hearing people that haven't used modern versions of Fish say that it's somewhat different from Bash and strays from POSIX compatibility quite a bit. While the latter is true, Fish has added many bash-isms over the years, so most scripting idioms you're familiar with will work there too.

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    • [–] 2 points 1 year ago

    By some sheer coincidence, I searched this topic today. I’ve been a consistent user of the parenthesis expansion, but never thought of why I preferred one or the other.

    I suppose the primary advantage is that $() will expand in a consistent way. You can even nest quotes and more expansions in one, while you’d struggle the same with backtick notation.

    So I’ll just keep using parentheses.

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