How can I use environment variables in body of a curl PUT request?

问题

I want to do a curl request which uses environment variables in the body:

curl -XPUT http://${HOST}/create -d'{"user":"${USER}"}'

In this request, ${HOST} is correctly replaced by the environment variable, but ${USER} is not. How can I replace ${USER} as well?

回答1:

Shell parameter expansion doesn't take place within single quotes. You can close the single quotes and start new double-quotes for the expansion:

curl -XPUT http://${HOST}/create -d'{"user":"'"${USER}"'"}'

Or you could use double-quotes instead:

curl -XPUT http://${HOST}/create -d"{\"user\":\"${USER}\"}"

In both cases, you need to be able to trust that $USER doesn't contain " - you might want to sanitize it first:

# This is a Bash extension to POSIX
USER=${USER//\"}

来源：https://stackoverflow.com/questions/48867599/how-can-i-use-environment-variables-in-body-of-a-curl-put-request