ICloud – Path to user directory when username is unknown

Test the output of uname; it will be Darwin on OS X and Linux on Linux.

if [[ $(uname) == Darwin ]]; then
    export PATH="$HOME/SW/bin_mac:$PATH"
fi

Alternately, you could just add an appropriate directory on each machine, which will be useful if you find yourself needing a separate Linux bin directory as well in the future.

export PATH="$HOME/SW/bin_$(uname):..."

and either mv or ln -s your bin_mac to bin_Darwin; then you can create a bin_Linux directory in the future if you need it, and it'll just work.

(You could also test $HOSTTYPE, which is set by bash, but it contains more information than you're likely to need.)

Honestly the best option is to just read the description in the App Store, the developer's website, and any reviews you can find. There's nothing in the App Store metadata that will tell you whether it uses iCloud or not.