bash – escaping variables for use within commands

Escaping quotes within variables is always painful in bash (somehow) – e.g.


and it’s not obvious that you’d need to write e.g.


(at least to me).

Thankfully a bash built in magical thing can be used to do the escaping for you.

In my case, I need to pass a ‘PASSWORD’ variable through to run within a container. The PASSWORD variable needs escaping so it can safely contain things like ; or quote marks (” or ‘).

e.g. docker compose run app /bin/bash "echo $PASSWORD > /some/file"

or e.g. ssh user@server “echo $PASSWORD > /tmp/something”

The fix is to use the ${PASSWORD@Q} variable syntax – for example:



ssh user@server “echo $FOO > /tmp/something”

This will fail, with something like : “bash: -c: line 1: unexpected EOF while looking for matching `''

As she shell at the remote end it seeing echo bar'"baz and expects the quote mark to be closed.

So using the @Q magic –

ssh user@server “echo ${FOO@Q} > /tmp/something”

which will result in /tmp/something containing “bar’”baz” which is correct.

See also



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