As of 2017, the source-code (runner.py) did this:
term = os.environ.get('TERMCMD', os.environ.get('TERM')) if term not in get_executables(): term = 'x-terminal-emulator' if term not in get_executables(): term = 'xterm' if isinstance(action, str): action = term + ' -e ' + action else: action = [term, '-e'] + action so you should be able to put any xterm-compatible program name in TERMCMD. However, note the use of -e (gnome-terminal doesn't match xterm's behavior). If you are using Debian/Ubuntu/etc, the Debian packagers have attempted to provide a wrapper to hide this difference in the x-terminal-emulator feature. If that applies to you, you could set TERMCMD to x-terminal-emulator.
Followup - while the design of the TERMCMD feature has not changed appreciably since mid-2016, the location within the source has changed:
That is implemented in get_term:
def get_term(): """Get the user terminal executable name. Either $TERMCMD, $TERM, "x-terminal-emulator" or "xterm", in this order. """ command = environ.get('TERMCMD', environ.get('TERM')) if shlex.split(command)[0] not in get_executables(): command = 'x-terminal-emulator' if command not in get_executables(): command = 'xterm' return command which uses x-terminal-emulator as before.
There is a related use of TERMCMD in rifle.py, used for executing commands rather than (as asked in the question) for opening a terminal. Either way, the key to using ranger is x-terminal-emulator, since GNOME Terminal's developers do not document their command-line interface, while Debian developers have provided this workaround.
Quoting from Bug 701691 – -e accepts only one term; all other terminal emulators accept more than one term (which the developer refused to fix, marking it "not a bug"):
Christian Persch 2013-06-06 16:02:54 UTC
There are no docs for the gnome-terminal command line options.