- To run a custom function right before a command runs, you can use the [`DEBUG` trap mechanism](https://jichu4n.com/posts/debug-trap-and-prompt_command-in-bash/). 然而，你**必須**在初始化 Starship *之前* 對 DEBUG 訊號設下trap！ Starship 可以保留 DEBUG trap 的數值，但是如果該 trap 在 starship 啟動後被被覆寫，某些功能會損壞。
PowerShell does not have a formal preexec/precmd framework like most other shells. Because of this, it is difficult to provide fully customizable hooks in `powershell`. 然而，Starship 有提供給你有限的能力來插入你自己的函式到渲染提示字元的程序中：
Create a function named `Invoke-Starship-PreCommand`
```powershell
functionInvoke-Starship-PreCommand{
$host.ui.Write("🚀")
}
```
## Change Window Title
Some shell prompts will automatically change the window title for you (e.g. to reflect your working directory). Fish even does it by default. Starship does not do this, but it's fairly straightforward to add this functionality to `bash` or `zsh`.
First, define a window title change function (identical in bash and zsh):
Some shells support a right prompt which renders on the same line as the input. Starship can set the content of the right prompt using the `right_format` option. Any module that can be used in `format` is also supported in `right_format`. The `$all` variable will only contain modules not explicitly used in either `format` or `right_format`.
Note: The right prompt is a single line following the input location. To right align modules above the input line in a multi-line prompt, see the [fill module](/config/#fill).
`right_format` is currently supported for the following shells: elvish, fish, zsh.
### 範例
```toml
# ~/.config/starship.toml
# A minimal left prompt
format="""$character"""
# move the rest of the prompt to the right
right_format="""$all"""
```
Produces a prompt like the following:
```
▶ starship on rprompt [!] is 📦 v0.57.0 via 🦀 v1.54.0 took 17s
Style strings are a list of words, separated by whitespace. The words are not case sensitive (i.e. `bold` and `BoLd` are considered the same string). Each word can be one of the following:
where `<color>` is a color specifier (discussed below). `fg:<color>` and `<color>` currently do the same thing, though this may change in the future. `inverted` swaps the background and foreground colors. The order of words in the string does not matter.
The `none` token overrides all other tokens in a string if it is not part of a `bg:` specifier, so that e.g. `fg:red none fg:blue` will still create a string with no styling. `bg:none` sets the background to the default color so `fg:red bg:none` is equivalent to `red` or `fg:red` and `bg:green fg:red bg:none` is also equivalent to `fg:red` or `red`. It may become an error to use `none` in conjunction with other tokens in the future.
