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Customizing Zsh Prompt

macOS 10.15 Catalina changed default Terminal from bash to zsh. When I first moved I tried Powerline extension but it was always a bit slow and really I all I need is a custom prompt. So today I revisited this and created a custom prompt for Zsh and learned a little along the way.

First I create an empty ~/.hushlogin to suppress the status message at the start of each Terminal session.

touch ~/.hushlogin

Prompt expansion can be used to customize the experience. The default prompt in zsh is %n%m%#.

  • %n username
  • %m hostname
  • %# shell state, # when privileges, otherwise %

So my default login prompt would show

dcauldwell@dcauldwell-a01 ~ %

PROMPT is variable so can be be set interactively give you immediate feedback and when you’re happy add to a startup script like ~/.zshrc so it loads automagically every time.

The options I choose to set:

  • %(?.%F{green}√.%F{red}?%?) will show previous Exit Code
  • %F{blue} defines foreground colour
  • %/ current working directory
  • %F{cyan} defines foreground colour
  • %# shell state

Zsh ships with a framework for getting information from version control systems, called vcs_info. When working within Git repositories in Terminal its useful to know which is active branch your editing.

We make the vcs_info framework by loading it:

autoload -Uz vcs_info

Run vcs_info just before a prompt is displayed (precmd)

precmd_vcs_info() { vcs_info }
precmd_functions+=( precmd_vcs_info )

Enable option for PROMPT_SUBST which turns on command substitution in the prompt:

setopt prompt_subst

We can then call its methods and consume within prompt, my new ~/.zshrc file looks like:

cat ~/.zshrc
autoload -Uz vcs_info
precmd_vcs_info() { vcs_info }
precmd_functions+=( precmd_vcs_info )
setopt prompt_subst
PROMPT='%(?.%F{green}√.%F{red}?%?)%F{blue} %/ %F{yellow}${vcs_info_msg_0_}%F{magenta} %# '

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