How to use variables in commands with backticks?

[PotatoesFall]

I read the README and couldn't find this. If I missed it, apologies.

In Makefile, I could do this:

GIT_COMMIT := $(shell git rev-parse --short HEAD)
GIT_TIME := $(shell git show -s --format=%ci $(GIT_COMMIT) | tr -d '\n')

In just, I understand that backticks can be used to save the output of a command:

GIT_COMMIT := `git rev-parse --short HEAD`
GIT_TIME := `git show -s --format=%ci $(GIT_COMMIT) | tr -d '\n'`

however, the second command fails with /usr/bin/sh: GIT_COMMIT: command not found

The {{}} syntax also doesn't work here, how can I use a variable in a command?

[runeimp]

My guess is that all or multiple lines like that are processed concurrently or at least not in order. Though @casey would know for sure. 😇

[casey]

So a few things are preventing this from working. First, just variables are distinct from shell variables, so you'll need to use the export keyword to export them:

export GIT_COMMIT := `git rev-parse --short HEAD`
export GIT_TIME := `git show -s --format=%ci $(GIT_COMMIT) | tr -d '\n'`

However, assignments are not processed in the order that they appear in a source file, so exported variables aren't available in backticks within the same scope, so GIT_COMMIT still wouldn't be available to the backtick assigned to GIT_TIME.

Hopefully we'll eventually support some kind of syntax that allows this, perhaps #799 or #822, but it might be a while! Sorry I don't have better news!

[PotatoesFall]

Ah okay that's clear, thanks. I'm sure I'll find another solution for my problem :)

[melMass]

Sorry to bump an old issue but just to be sure, this is not possible to escape variables directly either right?

root := `{{justfile_directory() / ".."}} | path expand`

(I use nushell here but you can replace the idea with realpath {{justfile_directory() / ".."}

EDIT: actually in my case the execution pwd in in fact justfile_directory.. so unrelated but this works fine: root := `".." | path expand`

[casey]

That's correct, interpolations in backticks aren't supported.

[pniederlag]

to bad... still true in 2024 ?