Nim: How to read environment variables

Nim: How to read environment variables

Reading environment variables is a simple way to enable runtime configuration of an application or script. Within Nim there’s two functions to get familiar with for reading values from the environment.

if getEnv("MY_VAR") == "1":
  echo "Got it!"
else:
  echo "Nope :("

This gets the value of MV_VAR (the equivalent of $MY_VAR from your shell). If the value is unset getEnv will return an empty string. Or, alternatively, you can provide a second argument to getEnv to specify the default value to us if your variable is unset:

if getEnv("MY_VAR", "is unset") == "is unset":
  echo "Nope :("

If you need to differentiate between a truly unset value and one that has inherited the default value then there is existsEnv:

if existsEnv("MY_VAR"):
  echo "This is set"
else:
  echo "This is not set"

Published: 21/03/2022