Use env variables with System.cmd or Ports?

What makes you say this? It’s a well defined library that could be considered complete. It’s not like the *nix CLI is a moving target that the library needs to be updated to work with

That’s just my personal opinion. I’m uncomfortable using it in production for what it the app I would use it in does. This also isn’t just for *nix, the app I would use this in is cross platform. I’m not going to use Porcelain, which is why I’m trying to figure out how to do it with System.cmd or Ports.

Also, it’s a matter of getting this past management as well. I can tell you right now my managers wouldn’t approve the use of a library that isn’t actively kept up.

If you look at the documentation for opening ports in the erlang library, you will find an env option. That is where you would set the environment. You might just have to pass the current environment there to add the options you want.

@isaacsanders I saw that in the otp docs and in the elixir Ports docs, but that doesn’t look it’s usable for existing env variables, just for passing a env variable at the time of opening the port. I could be wrong though.

Also, I would advise just using the underlying port infrastructure in Erlang’s and Elixir’s standard libraries if Porcelain makes you uncomfortable.

If you are trying to get a subset of your environment sent to the port, I would do so explicitly. I am under the impression from what you have posted that it doesn’t look at parameters in your shell, but requires you to set the env for the shell it creates.

@isaacsanders so if I’m understanding you correctly you mean this?:

iex(11)> System.cmd("/bin/echo", ["$GOPATH"], env: [{"$GOPATH", "/Users/rlthompson/go"}])
{"$GOPATH\n", 0}

However that doesn’t appear to work either.

Try:

iex(2)> System.cmd("env", [], env: [{"GOPATH", "/Users/rlthompson/go"}])

This shows that it exists in the env.

I think that to get further, you might need a shell script around it.

I tried:

System.cmd("/bin/echo", ["$GOPATH"], env: [{"GOPATH", "/Users/rlthompson/go"}])

and

System.cmd("/bin/echo $GOPATH", [], env: [{"GOPATH", "/Users/rlthompson/go"}])

Neither giving a desired result.

This works:

iex(1)> System.cmd("sh", ["test.sh"], env: [{"GOPATH", "/Users/rlthompson/go"}])
{"/Users/rlthompson/go\n", 0}

test.sh:

echo $GOPATH