Set the command to be used to create a new shell. This overrides the value of the environment variable
$SHELL. This is useful if you'd like to run a tty-enhancer which is expecting to execute the program specified in
$SHELL. If the command begins with a ‘-’ character, the shell will be started as a login-shell.
defshellis currently a synonym to the
Set the title for all shells created during startup or by the C-a C-c command. See Naming Windows, for details about what titles are.