Open an app in fullscreen via Terminal
Here it is:


  /usr/bin/osascript -e 'tell application "Safari"' -e "activate" -e 'tell application "System Events"' -e 'keystroke "f" using {control down, command down}' -e "end tell" -e "end tell"


Here it is in a clearer form (but you can't run it this way):

/usr/bin/osascript -e "tell application \"Safari\"" 
-e "activate"
-e "tell application \"System Events\""
-e "keystroke \"f\" using {control down, command down}"
-e "end tell"
-e "end tell"


And this is it as formatted AppleScript:

tell application "Safari"
    activate
    tell application "System Events"
        keystroke "f" using {control down, command down}
    end tell
end tell


It works by first opening a Safari window if one is not currently open. Then it simulates the Control ⌃-Command ⌘-F keystroke which tells the Safari window to become full screen.

If you want to make the window the max-size it can be without becoming full screen (i.e. taking up all the space below the menu bar at the top):

tell application "Finder"
    set desktopSize to bounds of window of desktop
end tell

tell application "Safari"
    activate
    set bounds of window 1 to desktopSize
end tell


Which would become this in Terminal:


  /usr/bin/osascript -e "tell application \"Finder\"" -e "set desktopSize to bounds of window of desktop" -e "end tell" -e "tell application \"Safari\"" -e "activate" -e "set bounds of window 1 to desktopSize" -e "end tell"


For Chrome, do this:

tell application "Google Chrome"
    activate
    make new window
    tell application "System Events"
        keystroke "f" using {control down, command down}
    end tell
end tell


So it would be this in Terminal:


  /usr/bin/osascript -e "tell application \"Google Chrome\"" -e "activate" -e "make new window" -e "tell application \"System Events\"" -e "keystroke \"f\" using {control down, command down}" -e "end tell" -e "end tell"


Hope this helps!