Just Programmer's Manual

Setting Variables in a Recipe

Recipe lines are interpreted by the shell, not just, so it’s not possible to set just variables in the middle of a recipe:

foo:
  x := "hello" # This doesn't work!
  echo {{x}}

It is possible to use shell variables, but there’s another problem. Every recipe line is run by a new shell instance, so variables set in one line won’t be set in the next:

foo:
  x=hello && echo $x # This works!
  y=bye
  echo $y            # This doesn't, `y` is undefined here!

The best way to work around this is to use a shebang recipe. Shebang recipe bodies are extracted and run as scripts, so a single shell instance will run the whole thing:

foo:
  #!/usr/bin/env bash
  set -euxo pipefail
  x=hello
  echo $x