Tool to automatically rewrite a bash script with proper quoting?

Question

I'm contemplating to make all bash scripts of a large codebase shellcheck compliant, but the task is overwhelming, because too many developers have historically ignored rule number one of all shell scripting: always use quotes.

It would be helpful if there was a tool that could fix at least the quoting. I would then be able to fix the rest by hand. My regex didn't cut it, because only variables not already in a string must be quoted.

Sample input:

echo "Removing $a ${b} $(c $(c)) `d $d` ${10} $@ now"
rm -rf $a ${b} $(c $(c)) `d $d` ${10} $@

Sample output:

echo "Removing $a $b $(c "$(c)") `d "$d"` ${10} $@ now"
rm -rf "$a" "$b" "$(c "$(c)")" "$(d "$d")" "${10}" "$@"

It doesn't have to fix all the above, and it doesn't even have to be flawless (though that would be really nice), but it has to be right more often than not to be useful.

---

Here is my naïve regex that didn't cut it:

s:([^"])\$\{([_A-Za-z0-9]+)\}([^"]|$):\1"\$\2"\3:g

It transforms ${identifier} to "$identifier", except when immediately preceded or followed by a quote, but fails to detect if we are deeper within the string.

Answer 1

WPomier beat me to it, but I did my own as well (because I wanted to):
https://github.com/anordal/shellharden

It acts as a syntax highlighter, until you give it the --transform option.

Answer 2

This is not an existent tool, but a little program in C, that it can help you as a base to get what you want.

You can see it here.

Example:

$ cat script.sh
echo "Removing $a ${b} $(c $(c)) `d $d` ${10} $@ now"
rm -rf $a ${b} $(c $(c)) `d $d` ${10} $@

$ checkshellvar < script.sh
echo "Removing $a ${b} $(c $(c)) `d $d` ${10} $@ now"
rm -rf "$a" "${b}" "$(c "$(c)")" "$(d "$d")" "${10}" "$@"

Disclaimer: The program achieves your sample output, but I did it in my coffee break, so don't expect too much ;-)

Note: Despite this program, I totally belieave that the quotes in shell scripting has a meaning, and their absence or the use of single or double quotes is perfectly valid depending on circumstances.