Understand variable place holder for curl command in Dockerfile I am learning about Dockerfile and had not worked with curl before. I am trying to understand line 26 in this Dockerfile . && bash -c 'curl " > /home/meteorapp/meteorapp/build/required-node-linux-x64.tar.gz' \ Is `$(<.node_version.txt)` means that some text I have to come up with as the value it expects or it is used as is, part of the command?

That means you need to have a file named `.node_version.txt`. In that file should be version number of node that you want. For example: `v4.6.0` or `latest`. To see valid version strings go to <

What happens is that this construct `$(<.node_version.txt)` is replaced with the contents of the file.

This line





becomes





The construct `$(