Bash export variables but only for current command

Question

I want to load some environment variables from a file before running a node script, so that the script has access to them. However, I don't want the environment variables to be set in my shell after the script is done executing.

I can load the environment variables like this:

export $(cat app-env-vars.txt | xargs) && node my-script.js

However, after the command is run, all of the environment variables are now set in my shell.

I'm asking this question to answer it, since I figured out a solution but couldn't find an answer on SO.

Answer 1

This is what the env command is for:

env - run a program in a modified environment

You can try something like:

env $(cat app-en-vars.txt) node my-script.js

This (and any unquoted $(...) expansion) is subject to word splitting and glob expansion, both of which can easily cause problems with something like environment variables.

A safer approach is to use arrays, like so:

my_vars=(
  FOO=bar
  "BAZ=hello world"
  ...
)
env "${my_vars[@]}" node my-script.js

You can populate an array from a file if needed. Note you can also use -i with env to only pass the environment variables you set explicitly.

---

If you trust the .txt's files contents, and it contains valid Bash syntax, you should source it (and probably rename it to a .sh/.bash extension). Then you can use a subshell, as you posted in your answer, to prevent the sourced state from leaking into the parent shell:

( source app-env-vars.txt && node my-script.js )