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--- |
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title: Building a ZSH prompt |
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tags: |
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- Linux |
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- ZSH |
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description: There are many frameworks out there to help you build a prompt, I thought I'd see how far I could get without one. |
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date: 2020-03-24 |
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draft: true |
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--- |
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Until recently, I was using [oh-my-zsh](https://github.com/ohmyzsh/ohmyzsh) with the [Power Level 9k](https://github.com/Powerlevel9k/powerlevel9k) prompt. |
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In part of my effort to understand how different parts of my system works, and to reduce my reliance on some libraries, I decided to see if I could get what I needed without them. In this blog post, I am going to focus on my prompt configuration. |
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If you want to follow along, my configuration can be found in [my dotfiles](https://github.com/Jab2870/dotfiles/blob/master/shells/zsh/includes/promptconfig.zsh). |
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My prompt currently looks something like this: |
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## Basics |
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Zsh simply prints the variables `PROMPT` and `RPROMPT` when drawing the left and right prompts respectively. `PROMPT` is roughly equivalent to the `PS1` variable in bash. |
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By setting the variable, you can change how the prompt works. E.g. |
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``` |
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oldPrompt $ PROMPT="new prompt > " |
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new prompt > ls |
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Documents Downloads GitRepos |
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new prompt > █ |
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``` |
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## ZSH Hooks |
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Zsh has a concept called hooks. These allow you to run a function (or functions) automatically at certain times. |
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For the purposes of setting my prompt, I want to run a function to set `PROMPT` and `RPROMPT` before the prompt is drawn. This can be done with the `precmd` hook. |
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```zsh |
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set_prompts(){ |
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PROMPT="$ " |
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RPROMPT="" |
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} |
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zle -N set_prompts |
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autoload -U add-zsh-hook |
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add-zsh-hook precmd set_prompts |
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``` |
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This defines a function `set_prompts` and it will be run just before the prompt is drawn, every time. We can therefore use it to build the prompt. |
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## Drawing segments |
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I like the arrow style that was made popular by [Powerline](https://github.com/powerline/powerline). To achieve this, you will need a font that contains the powewline glyphs. If you don't have one, I highly recommend the [Nerd Fonts](https://www.nerdfonts.com/) project that aggregates a lot of icons as well as the powerline symbols. It even includes a script that allows you to add them to your favourite font. |
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## Exit Code |
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In ZSH (and most other shells), the exit code of the previous command is available in the special `$?` variable. If we want the exit code of the last command run, we need to assign this to a variable first. |
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```bash |
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# Get the return status of the previous command |
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local RETVAL=$? |
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``` |
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## Git |
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I use Git a lot. It is useful to tell, at a glance, which branch I'm on, which tag I'm on and what the state of repository is. The function is quite simple: |
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```bash |
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prompt_git(){ |
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local repoTopLevel="$(command git rev-parse --show-toplevel 2> /dev/null)" |
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if [ -n "$repoTopLevel" ]; then |
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local branch="$(git branch --show-current 2> /dev/null)" |
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local tag="$(git describe --tags --exact-match HEAD 2> /dev/null)" |
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local color="green" |
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local ret="" |
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[ -n "$branch" ] && ret="$branch " |
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[ -n "$tag" ] && ret+="$tag " |
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[ -n "$ret" ] || ret="$(git rev-parse --short HEAD 2> /dev/null)" |
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local repoTopLevel="$(command git rev-parse --show-toplevel 2> /dev/null)" |
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local untrackedFiles=$(command git ls-files --others --exclude-standard "${repoTopLevel}" 2> /dev/null) |
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local modified=$(command git diff --name-only 2> /dev/null) |
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local staged=$(command git diff --staged --name-only 2> /dev/null) |
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if [ -n "$untrackedFiles" ]; then |
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ret+=" " |
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color="orange1" |
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fi |
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if [ -n "$modified" ]; then |
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ret+=" " |
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color="orange1" |
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fi |
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if [ -n "$staged" ]; then |
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ret+=" " |
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color="orange1" |
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fi |
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fi |
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ret="$(echo "$ret" | sed -e 's/ *$//')" |
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echo "$ret" |
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echo "$color" |
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} |
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``` |
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