How to open an image file from bash in Mac

Short answer: whichever suits you.

If your Unix background is mainly from Linux, you’re probably used to GNU commands. As you’ve noticed, they can be different from other Unix/Unix-based operating systems. Depending on how complex your scripts are, you can either:

• make simple changes (like using ls -R . instead of ls . -R), which will work in most (if not all) Unix/Unix-based system and not only on GNU-based ones,

• or install the GNU utilities from MacPorts if you think that there’d be too many/complex changes, or if you prefer to stick to the GNU commands you’re already used to.

If you want to take some time and write portable scripts, do it. If you think that’s not worth it, then don’t. Just bear in mind that not every Unix/Unix-based system uses GNU by default.

I've found a way. Does anyone know a simpler way?

tell application "Preview"
        activate
end tell

tell application "System Events"
        key down {command}
        key down {shift}
        keystroke "f"
        key up {shift}
        key up {command}
end tell

I wish I could do simply "osascript -e 'application "Preview" to fullscreen'.