Bash Quoting

For years I’ve been frustrated by my inablity to puzzle out how to write this in bash:

H=$(dirname $0)

so it’s safe if $0 has spaces in it.

Clearly

H="$(dirname $0)"

is better, but still the $0 isn’t usefully quoted.

I finally complained to the shellcheck author that this should be in the FAQ, though there isn’t a FAQ. And he assured me if you do it right it isn’t a problem.  He also happened to mention the answer:

H="$(dirname "$0")"

I complained that just because it wasn’t a question if you’d ask if you knew the answer didn’t mean that it wasn’t a commonly asked question.  So he added (or updated) a wiki page to say that the $(…) creates a new “context”.

So there you go.

One thought on “Bash Quoting

  1. Caleb

    Wow, yeah, I struggle with quote escaping a lot — does this single-quote need to be escaped, what about these nested double-quote — and that is not at all obvious. I suppose ‘context’ is a decent term for this, but I fail fast at keeping a stack of context in my head. Command redirection might be apropos, given that pipes are easier to reason about.

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