Cross-Platform Scripting!

So I wanted to make a script that could be ran on both windows and unix based systems to help with distributing things on multiple platforms, all in 1 script without any changes to said script.

To do this, I first tried to use the “ErrorActionPreference” enviromental variable.

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#!/bin/bash
$ErrorActionPreference='SilentlyContinue' # We exploit that this has no meaning in a unix enviroment, but does in the windows powershell
# Bash script here
cal
# This will (obviously) throw an error on windows, but since we silently continue, it executes the below on windows without error
# but stops due to error on linux
New-Item -Path 'C:\Users\ghostdog\Desktop\Test.txt' -ItemType File

At first, this seems to work, however, if we look at any command that is shared between the operating systems, we can see this fails, such as the following:

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#!/bin/bash
$ErrorActionPreference='SilentlyContinue'

cal
echo "This should only execute on unix!"

New-Item -Path 'C:\Users\ghostdog\Desktop\Test.txt' -ItemType File

This, obviously, leads to powershell outputting that echo.

My first thought to fix this, would be to simply modify the third and forth line to cal && echo "Unix!", but, that seems to throw an error not caught by the powershell enviroment variable we set earlier in some versions. To fix this, i need a universal logical AND.

This, however, proved to be futile, as there was a much simpler solution:

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:; echo "I'm on unix!!!" #
:; echo "I'm on unix!!!" #
ECHO OFF 
ECHO Hi Windows
PAUSE

Or even better:

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::; echo "Unix!" ; exit
ECHO OFF
ECHO Hi
PAUSE

We then save this as a batch file, and when we execute it on unix, it says “Unix!” but on windows, simply says “Hi”.