Shims

There are several ways for the mise context (dev tools, environment variables) to be loaded into your shell:

• mise activate (also called "mise PATH activation") where mise updates your PATH and other environment variables every time your prompt is displayed.
• mise activate --shims which uses shims to load dev tools.
• Using mise x|exec or mise r|run for ad-hoc commands or tasks (see "neither shims nor PATH").

This page will help you understand the differences between these methods and how to use them. In particular, it will help you decide if you should use shims or mise activate in your shell.

Overview of the mise activation methods

PATH activation

Mise's "PATH" activation method updates environment variables every time the prompt is displayed. In particular, it updates the PATH environment variable, which is used by your shell to search for the programs it can run.

INFO

This is the method used when you add the echo 'eval "$(mise activate bash)"' >> ~/.bashrc line to your shell rc file (in this case, for bash).

For example, by default, your PATH variable might look like this:

echo $PATH
/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin

If using mise activate, mise will automatically add the required tools to PATH.

PATH="$HOME/.local/share/mise/installs/python/3.13.0/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin"

In this example, the python bin directory was added at the beginning of the PATH, making it available in the current shell session.

While the PATH design of mise works great in most cases, there are some situations where shims are preferable. This is the case when you are not using an interactive shell (for example, when using mise in an IDE or a script).

Shims

WARNING

mise activate --shims does not support all the features of mise activate.
See shims vs path for more information.

When using shims, mise places small executables (shims) in a directory that is included in your PATH. You can think of shims as symlinks to the mise binary that intercept commands and load the appropriate context.

ls -l ~/.local/share/mise/shims/node
# [...] ~/.local/share/mise/shims/node -> ~/.local/bin/mise

By default, the shim directory is located at ~/.local/share/mise/shims. When installing a tool (for example, node), mise will add some entries for every binary provided by this tool in the shims directory (for example, ~/.local/share/mise/shims/node).

mise use -g node@20
npm install -g [email protected]

~/.local/share/mise/shims/node -v
# v20.0.0
~/.local/share/mise/shims/prettier -v
# 3.1.0

To avoid calling ~/.local/share/mise/shims/node, you can add the shims directory to your PATH.

export PATH="$HOME/.local/share/mise/shims:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin"

This will effectively make all dev tools available in your current shell session as well as non-interactive environments.

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mise activate --shims is a shorthand for adding the shims directory to PATH.

How to add mise shims to PATH

The recommended way to add shims to PATH is to call mise activate --shims in one of your shell initialization file. For example, you can do the following:

bash

# note that bash will read from ~/.profile or ~/.bash_profile if the latter exists
# ergo, you may want to check to see which is defined on your system and only append to the existing file
echo 'eval "$(mise activate bash --shims)"' >> ~/.bash_profile # this sets up non-interactive sessions
echo 'eval "$(mise activate bash)"' >> ~/.bashrc       # this sets up interactive sessions

zsh

echo 'eval "$(mise activate zsh --shims)"' >> ~/.zprofile # this sets up non-interactive sessions
echo 'eval "$(mise activate zsh)"' >> ~/.zshrc    # this sets up interactive sessions

fish

echo 'mise activate fish --shims | source' >> ~/.config/fish/config.fish
echo 'mise activate fish | source' >> ~/.config/fish/fish.config

In this example, we use mise activate --shims in the non-interactive shell configuration file (like .bash_profile or .zprofile) and mise activate in the interactive shell configuration file (like .bashrc or .zshrc)

INFO

mise activate will remove the shims directory from the PATH so it's fine to call mise activate --shims in your shell profile file then later call mise activate in an interactive session.

• You can also decide to use only shims if you prefer, though this comes with some limitations.
• An alternative to mise activate --shims is to use export PATH="$HOME/.local/share/mise/shims:$PATH". This can be helpful if mise is not yet available at that point in time.

mise reshim

To force mise to update the content of the shims directory, you can manually call mise reshim.

Note that mise already runs a reshim anytime a tool is installed/updated/removed, so you don't need to use it for those scenarios. It is also done by default when using most tools such as npm.

mise reshim only creates/removes the shims. Some users sometimes use it as a "fix it" button, but it is only necessary if ~/.local/share/mise/shims doesn't contain something it should.

Do not add additional executable in the mise directory, mise will delete them with the next reshim.

Shims vs PATH

The following features are affected when shims are used instead of PATH activation:

• Env vars defined in mise are only available to mise tools
• Most hooks won't trigger
• The unix which command points to the shim, obscuring the real executable

In general, using PATH (mise activate) instead of shims for interactive situations is recommended.

The way activate works is every time the prompt is displayed, mise-en-place will determine what PATH and other env vars should be and export them. This is why it doesn't work well for non-interactive situations like scripts. The prompt never gets displayed so you have to manually call mise hook-env to get mise to update the env vars. (though there are exceptions, see hook on cd)

Env vars and shims

A downside of shims is that the environment variables are only loaded when a shim is called. This means if you set an environment variable in mise.toml, it will only be used run when a shim is called.

The following example only works under mise activate:

$ mise set NODE_ENV=production
$ echo $NODE_ENV
production

But this will work in either:

$ mise set NODE_ENV=production
$ node -p process.env.NODE_ENV
production

Also, mise x|exec and mise r|run can be used to get the environment even if you don't need any mise tools:

$ mise set NODE_ENV=production
$ mise x -- bash -c "echo \$NODE_ENV"
production
$ mise r some_task_that_uses_NODE_ENV
production

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In general, tasks are a good way to ensure that the mise environment is always loaded.

Hooks and shims

The hooks cd, enter, exit, and watch_files only trigger with mise activate. However preinstall and postinstall still work with shims because they don't require shell integration.

which

which is a command that a lot of users find great value in. Using shims effectively "break" which and cause it to show the location of the shim. A workaround is to use mise which will show the actual location. Some users prefer the "cleanliness" of running which node and getting back a real path with a version number inside of it. e.g:

$ which node
~/.mise/installs/node/20/bin/node

Performance

Truthfully, you're probably not going to notice a difference in performance when using shims vs. using mise activate.

• Since mise runs every time the prompt is displayed with mise activate, you'll pay a few ms cost every time the prompt is displayed. Regardless of whether you're actively using a mise tool, you'll pay that penalty every time you run any command. It does have some short-circuiting logic to make it faster if there are no changes, but it doesn't help much unless you have a very complex setup.
• shims have basically the same performance profile but run when the shim is called. This makes some situations better, and some worse.

If you are calling a shim from within a bash script like this:

for i in {1..500}; do
    node script.js
done

You'll pay the mise penalty every time you call it within the loop. However, if you did the same thing but call a subprocess from within a shim (say, node creating a node subprocess), you will not pay a new penalty. This is because when a shim is called, mise sets up the environment with PATH for all tools and those PATH entries will be before the shim directory.

In other words, which is better in terms of performance just depends on how you're calling mise. Really though most users will not notice a few ms lag on their terminal caused by mise activate.

The only difference between these would be that using hook-env you will need to call it again if you change directories but with shims that won't be necessary. The shims directory will be removed by mise activate automatically so you won't need to worry about dealing with shims in your PATH.

Neither shims nor PATH

There are many ways to load the mise environment that don't require either, chiefly: mise x|exec, mise r|run or mise en.

These will both load all the tools and env vars before executing something. This might be ideal because you don't need to modify your shell rc file at all and the environment is always loaded explicitly. Some might find this is a "clean" way of working.

The obvious downside is that anytime one wants to use mise they need to prefix it with mise exec|run. Though, you can easily alias them to mx|mr.

• This is what one prefers if they like things to be precise over "easy".
• Or perhaps if you're just wanting to use mise on a single project because that's what your team uses and prefer not to use it to manage anything else on your system. Using a shell extension for that use-case would be overkill.

This is the method Jeff uses

Part of the reason for this is I often need to make sure I'm on my development version of mise. If you work on mise yourself I would recommend working in a similar way and disabling mise activate or shims while you are working on it.

See How I use mise for more information.

Hook on cd

For some shells (bash, zsh, fish), mise hooks into the cd command, while in others, it only runs when the prompt is displayed. This relies on chpwd in zsh, PROMPT_COMMAND in bash, and fish_prompt in fish.

The upside is that it doesn't run as frequently but since mise is written in rust the cost for executing mise is negligible (a few ms).

Running several commands in a single line

If you run a set of commands in a single line like the following:

cd ~
cd ~/src/proj1 && node -v && cd ~/src/proj2 && node -v

If using mise activate, in shell without hook on cd, this will use the tools from ~, not from ~/src/proj1 or ~/src/proj2 even after the directory changed.

This is because, in these shells mise runs just before your prompt gets displayed whereas in others, it hooks on cd. Note that shims will always work with the inline example above.

Using mise in rc files

rc files like .zshrc are unusual. It's a script but also runs only for interactive sessions. If you need to access tools provided by mise inside of an rc file you have 2 options:

hook-env

eval "$(mise activate zsh)"
eval "$(mise hook-env -s zsh)"
node some_script.js

shims

eval "$(mise activate zsh --shims)" # should be first
eval "$(mise activate zsh)"
node some_script.js