Bash tokenizing quoted string with spaces as individual words

Question

I\'m trying to execute the following commands:

mkdir \'my dir\'
CMD=\"ls \'my dir\'\"
RESULT=$($CMD)

This results in:

ls: \'my:         


        

Answer 1

(Almost) all languages differentiate between code and data:

args="1, 2"
myfunc(args) != myfunc(1, 2)

The same is true in bash. Putting single quotes in a literal string will not make bash interpret them.

The correct way of storing a program name and arguments (aka a simple command) is using an array:

cmd=(ls 'my dir')
result=$("${cmd[@]}")

Bash will automatically split words on spaces unless you double quote, which is why your example sometimes appears to work. This is surprising and error prone, and the reason why you should always double quote your variables unless you have a good reason not to.

It's also possible to get bash to interpret a string as if it was bash code entirely, using eval. This is frequently recommended, but almost always wrong.