Set The asdf Package Version For A Single Shell

Generally when using asdf, I set the global version for a package/language to a good up-to-date default. And then I set local versions for specific projects which get written to the .tool-versions file.

There is another option that asdf supports for when you want to use a version without it being so sticky.

$ asdf shell postgres 12.3

$ psql --version
psql (PostgreSQL) 12.3

$ postgres --version
postgres (PostgreSQL) 12.3

With the shell command, I tell asdf to shim the specified package version just for this shell instance. If I switch back to another tab or open a new one, neither of them will have been impacted by this shell-constrained setting.

This is handy for a one-off situation where you want to try something at a specific version without impact the rest of your terminal session.