Bash Variable within string, within string

Question

So, I am trying to run a Python script from within a Bash script. The Python script takes one of its parameters in the form of a JSON string, which looks like this:

'[{"CONFIG":"SomeConfigID"}]' //there are other members available but this is all I need.

I would like to pass in a variable from the Bash script as a member of the JSON object. So, This is what I am doing:

'[{"CONFIG":"${CONFIG}"}]'

However, what I find is that the Python script fails because it does not recognise ${CONFIG}

For some reason, Bash is not replacing that expression with the value of the variable. I am unfamiliar with Bash, so this may simply be something obvious that I am missing. Can anybody help? Is there some other way to construct this JSON string that would not cause this problem?

In Bash, a variable within single quotes is treated as literal. To have its value expanded you need to double quote it. Thus, you must probably swap the quotes you are using: does "[{'CONFIG':'${CONFIG}'}]" work to you? — fedorqui
– fedorqui, Commented Feb 25, 2015 at 10:22

anubhava · Accepted Answer · 2015-02-25 10:22:36Z

4

Get the right quoting in place for shell expansion:

'[{"CONFIG":"'"${CONFIG}"'"}]'

As shell variable must not in single quote for shell to expand them.

Example:

CONFIG=foo
echo '[{"CONFIG":"'"${CONFIG}"'"}]'
[{"CONFIG":"foo"}]

answered Feb 25, 2015 at 10:22

anubhava

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