How to use environment variables for field name in DSL?

[YokojimaSkewers]

What I want to do is equal to

mlr put '$'"${FIELD_NAME}"' = hoge'

I want to do this with only one string like

mlr put '$ENV["FIELD_NAME"] = hoge'

but this does not work. Is there a way to do this?

[aborruso]

@YokojimaSkewers I think you can use the system functions

[YokojimaSkewers]

Thank you. I didn't know that.

[johnkerl]

@YokojimaSkewers do you mean this?

$ export FIELD_NAME=bar
$ echo x=abc | mlr put '$[ENV["FIELD_NAME"]] = "hoge"'
x=abc,bar=hoge

[YokojimaSkewers]

Thank you. This works fine and looks best.

[aborruso]

The related documentation https://miller.readthedocs.io/en/latest/reference-dsl-variables/#built-in-variables