Or, probably from 3.9 and later:
One particular "nice" feature makes up today's "Shell Hack": Interactive debugging, and tracing of shell scripts. Tracing means that the shell shows you which command it is about to execute, and you may run the command, skip over it or stop tracing.
To enable tracing, use the following command in the shell:
set interactive on
If this is put top in a shell script, for example into the startup-sequence (with an editor of your choice), the shell will prompt you for each command it is going to be executed. If you press RETURN, the shell will run the command. If you press N or DEL, the shell will skip over it. If you press ESC, the shell will abort tracing and execute the rest of the script without bothering you further. If you press Control+D, the script will be aborted.
