How to check if running in Cygwin, Mac or Linux?

Question

I have a shell script that is used both on Windows/Cygwin and Mac and Linux. It needs slightly different variables for each versions.

How can a shell/bash script de

Answer 1

# This script fragment emits Cygwin rulez under bash/cygwin
if [[ $(uname -s) == CYGWIN* ]];then
    echo Cygwin rulez
else 
    echo Unix is king
fi

If the 6 first chars of uname -s command is "CYGWIN", a cygwin system is assumed