How do you check if a command exists on windows?

[sanzoghenzo]

Hi there, first of all thanks for this wonderful tool!

I'm mostly a linux user, but some of my colleagues prefer to work on windows, so I'm trying to keep my tools as cross-platform as possible.

I would like to add a status check to skip the installation of tools already present (in my specific case they are python packages, but it can be anything).

How do you check if a command already exists on windows/powershell?

I tried to use Get-Command {{.COMMAND_NAME}} but it always executes the task.
I also tried something more fancy such as if(Get-Command {{.COMMAND_NAME}}) {Exit 0} else {Exit 1}, same result.

Am I missing something here?

Here is a minimal example:

version: '3'

tasks:
  install:package:
    label: 'install:{{.PACKAGE_NAME}}'
    vars:
      PACKAGE_NAME: '{{.PACKAGE_NAME}}'
      COMMAND_NAME: '{{default .PACKAGE_NAME .COMMAND_NAME}}'
    cmds:
      - "pip install {{.PACKAGE_NAME}}"
    status:
      - '{{if eq OS "windows"}}if(Get-Command {{.COMMAND_NAME}}) {Exit 0} else {Exit 1}{{else}}command -v {{.COMMAND_NAME}}{{end}}'

  install:pre-commit:
    cmds:
      - task: install:package
        vars:
          PACKAGE_NAME: pre-commit

  init:pre-commit:
    deps:
      - install:pre-commit
    cmds:
      - pre-commit install

  lint:
    deps:
      - init:pre-commit
    cmds:
      - pre-commit run --all

[andreynering]

I'm not on a Windows machine ATM to try things out.

This made me realize, though, that the which builtin is missing an implementation on our shell interpreter, and would be useful here to avoid any if/elses.

• interp: consider adding some coreutils as builtins mvdan/sh#93
• interp: support all Bourne shell (POSIX) builtins mvdan/sh#97

[sanzoghenzo]

Oh boy, I'm an idiot, I didn't even try to use command -v on windows! It is already in interp, and indeed it works!

As per the which command, according to this SO answer it is to be avoided since its implementation differs from OS to OS (some don't even have an exit code). command -v is enough and already built-in.

[sanzoghenzo]

Nevermind, as I stated in the reply to @andreynering , the builtin command -v works on windows and I didn't even try it.

I suppose I overlooked the explanation of the sh interpreter in the Getting Started section, and directly went to find a substitute for the command 😅

Thanks again for this great tool!