How to have a script work with "$@" or a default list of parameters while not breaking paths with whitespace?

It appears you can't set default parameters in an expansion of ${@:-...}, and "${@:-"$base/aaa" "$base/bbb"}" is expanded as a single string.

If you want to set default parameters you might want to do this:

base=$(dirname -- "$0")
# test explicitly for no parameters, and set them.
if [ "$#" -eq 0 ]; then
    set -- "$base/aaa" "$base/bbb"
fi

Then, the "$@" magically quoted parameter substitution can happen unabated:

touch -- "$@"

It IS possible to use several parameters in a default expansion ${@-...},

like this:

#!/bin/bash
base=$(dirname "$0")
arr=("$base/aaa" "$base/bbb")

touch "${@:-"${arr[@]}"}"

But only on shells that have arrays (ksh, zsh, bash, etc.).

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