[hmry]

Definitely. I would argue even in shell scripts it's not always great. Just thinking about all those times rm -rf "~/${configdir}" accidentally wiped someone's home directory because that unset variable was implicitly turned into an empty string, etc.

I would not want to use a language with a spongy type system for any code I'm distributing to other people But for quick one-off scripts that only I will use, it is quite convenient.

[1vuio0pswjnm7]

   test ! "${configdir}"||rm -rf "~/${configdir}"

   [ "${configdir}" ]&&rm -rf "~/${configdir}"

   test x"${configdir}" = x""||rm -rf "~/${configdir}"

   [ x"${configdir}" != x"" ]&&rm -rf "~/${configdir}"

This assumes NetBSD ash or Debian ash which is what I use. I write scripts for me, not for others and often end up using "quick one-off" scripts for years. After decades of using UNIX, I have never wiped a root directory accidentally (but there is still time). YMMV.

[nerdponx]

Sure, and in Zsh you can do `(( $+configdir ))` if you want to differentiate "unset" from "empty". But the fact that you need this check at all demonstrates the existence of a problem.

You can also set the "-u" option (in Zsh, `setopt no_unset`) which at least will cause your script to crash with an error if you happen to forget this check. But then you have to remember to set that option as well!

Lua has a similar-ish problem with undefined variables being `nil`, but for the most part Lua is also rather strictly typed, and that will typically end up causing some kind of error deep inside a function call, rather than doing something dangerous silently.

[samatman]

While what you say about Lua is true, undefined variables can be promoted to errors. An `__index` function can throw an error if a slot looked up on a table is nil, and the environment is just a table.

That's Lua for you. The semantic model is dead simple and easy to understand, and even though roughly no one wants typos to become variables, the semantics would have to be less minimal to accomplish this.

So instead, there's a mechanism, a more than adequate one, but one does have to use it.

[1vuio0pswjnm7]

Also

  test "${#configdir}" -lt 1||rm -rf "~/${configdir}"

  [ "${#configdir}" -gt 0 ]&&rm -rf "~/${configdir}"