I usually keep all of my dotfiles in a repo and share them across all of my machine. So when I had a couple of Bash alias' that were not working and environment variables that were different on my Macbook it was becoming a bit annoying.
So I started using OS conditionals inside my .bash_aliases and .bashrc files
if [[ $(echo $OSTYPE) == "linux-gnu" ]]; then
# Linux
elif [[ $(echo $OSTYPE) == "darwin"* ]]; then
# Mac OSX
fi
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