How to add a custom prompt to windows console

Cmder is an awsome package of software which replaces the default console cmd.exe or powershell on windows.

If you are in a git repo, you see the current branch in the prompt, colored in white if its clean or red if dirty. There are similar features for yarn, npm, ...

Sometimes you want to add the output of to the prompt too. This can be done like this:

In my case i wanted to see on which terraform workspace i am. with terraform you can do this by running terraform workspace show in your terraform directory. this would output something like

λ terraform workspace show
default

To do this you have to create a clink extension. Assuming that you installed cmder in C:\Program Files\Cmder you create a file called terraform.lua in C:\Program Files\Cmder\vendor\clink-completions

terraform.lua

local color = require("color")

local function is_terraform()
    for dir in io.popen([[dir ".\" /b /ad]]):lines() do 
        if dir == ".terraform" then
            return true
        end 
    end

    return false
end

local function terraform_prompt_filter()
    if is_terraform() then
        f = assert (io.popen ("terraform workspace show"))
        for line in f:lines() do
            terraform_context = '(workspace: ' .. line .. ')'
            if line == "production" then
                prompt_color = color.RED
            elseif line == "development" then
                prompt_color = color.GREEN
            else
                prompt_color = color.YELLOW
            end
            break
        end -- for loop
        f:close()
        terraform_context = color.color_text(terraform_context, prompt_color)
        clink.prompt.value = clink.prompt.value:gsub("\n", terraform_context .. "\n")
        return false
    end 
end

clink.prompt.register_filter(terraform_prompt_filter, 1)

this code checks if it is currently in a terraform directory by looking if the directory .terraform exists. it colors the workspace output in green if you are on development workspace, red if you are on production and yellow on all others. adapt the code for your needs.

i am sure that the lua code can be optimized, i am open for comments and enhancements.

links:

• cover image by Willi Heidelbach https://pixabay.com/en/puzzle-match-missing-hole-blank-693870/