[Help-bash] Why not make ${var@Q} the same as `printf %q' output?

[Clark Wang]

See following example:

$ var=123
$ echo ${***@Q}
'123'
$ printf '%q\n' $var
123
$
$ var='1 2 3'
$ echo ${***@Q}
'1 2 3'
$ printf '%q\n' "$var"
1\ 2\ 3
$

Any particular reason to implement them differently?

-clark

[Chet Ramey]

Post by Clark Wang
$ var=123
'123'
$ printf '%q\n' $var
123
$
$ var='1 2 3'
'1 2 3'
$ printf '%q\n' "$var"
1\ 2\ 3
$
Any particular reason to implement them differently?

It wasn't a great decision to use backslash quoting with printf %q, but
it's been that way for a long time and I'd rather not change it. The
transformation operators all use single quoting to quote when needed,
and I think that works better.