Control whether commands are displayed as they are executed. Valid options are:
on- Enable echoing of commands as they are executed in script files.
off- Disable echoing of commands as they are executed in script files.
on all- Enable echoing of commands as they are executed in script files and functions.
off all- Disable echoing of commands as they are executed in script files and functions.
If invoked without any arguments,
echotoggles the current echo state.