Shell tricks

A collection of shell utilities that build on mise.

Prompt colouring

In Zsh, add a prompt hook after your existing mise activate zsh setup. This example replaces the prompt with a blue marker when mise's environment state changes and a green marker otherwise. It leaves mise's activation functions intact:

# Put this after your existing mise activation in ~/.zshrc.
autoload -Uz add-zsh-hook
typeset -g _mise_prompt_diff="${__MISE_DIFF-}"

function _mise_prompt_colour {
  local previous_status=$?
  if [[ "${__MISE_DIFF-}" != "$_mise_prompt_diff" ]]; then
    PROMPT='%F{blue}❱ %f'
  else
    PROMPT='%F{green}❱ %f'
  fi
  _mise_prompt_diff="${__MISE_DIFF-}"
  return "$previous_status"
}

add-zsh-hook -d precmd _mise_prompt_colour
add-zsh-hook precmd _mise_prompt_colour

__MISE_DIFF is internal state, so treat this as a customization to maintain when upgrading mise. To undo it, remove _mise_prompt_colour with add-zsh-hook -d precmd _mise_prompt_colour and restore your usual PROMPT or prompt theme.

Current configuration environment in powerline-go prompt

powerline-go's shell-var segment can be used to display the value of an environment variable in the prompt. The current mise configuration environment, MISE_ENV, is a good candidate for this.

Mostly, it works as you would expect: include shell-var in -modules, pass -shell-var MISE_ENV -shell-var-no-warn-empty in the arguments, and make sure MISE_ENV is exported so powerline-go can see it.

If your version of powerline-go warns when MISE_ENV is unset, ensure the variable is defined while preserving any selection made before the shell started:

export MISE_ENV="${MISE_ENV-}"

This displays the exported MISE_ENV value. Environments chosen only for one command with mise -E, or platform environments selected by auto_env, are not persistent changes to that shell variable.

Inspect what changed after mise hook

For ordinary troubleshooting, start with mise config, mise doctor, or MISE_DEBUG=1 mise env. If you need to inspect shell bookkeeping itself, __MISE_DIFF and __MISE_SESSION currently contain base64-encoded, zlib-compressed MessagePack data.

The following Bash/Zsh helper requires Python and the msgpack package. Create an isolated Python environment for the decoder:

python3 -m venv ~/.cache/mise-env-inspect
~/.cache/mise-env-inspect/bin/python -m pip install msgpack

function mise_parse_env {
  printf '%s' "$1" | "$HOME/.cache/mise-env-inspect/bin/python" -c '
import base64, pprint, sys, zlib
import msgpack
value = sys.stdin.read().strip()
if not value:
    raise SystemExit("No mise state was supplied; activate mise first")
payload = zlib.decompress(base64.b64decode(value + "=" * (-len(value) % 4)))
pprint.pprint(msgpack.unpackb(payload, raw=False), sort_dicts=False)
'
}

Use it in an activated shell:

mise_parse_env "$__MISE_DIFF"
mise_parse_env "$__MISE_SESSION"

This format is an implementation detail, not an API. The decoded data can contain environment values, including secrets; inspect it locally and redact it before sharing diagnostic output.