9 Ways to NRT, part 7: Creating an interactive NRT parser
Welcome to Part 7 of 9 Ways to NRT!
NRT by itself does not have a built-in interactive mode, and it doesn't need one. It is simple enough to implement an interactive environment built the Unix way. I call it NRTi.
NRTi can be found in the part 7 folder on the nineways github.
To run NRTi, you must have NRT (duh), Csound, and rlwrap installed.
NRTi has two components: the "sender" and the "reciever". To start the reciever, run this command:
sh nrti-reciever.sh | csound simple.csd
In the csound file, you will most likely have to change some of the CsOptions and samplerate to match your computers setup (unless you happen to be running on Linux with Jack running at a samplerate of 96kHz.)
The reciever should now be waiting patiently for input from the sender.
To start the sender, run this command:
rlwrap sh nrti-sender.sh
A command prompt should now appear. Type some nrt (like "drmfs") and hear Csound play it back.
How it Works
NRTi uses a named pipe (literally named pipe in this instance) to send and recieve information. When the reciever is started, it creates a pipe using the mkfifo command. Information from that pipe is then piped to NRT. NRT output is converted to a Csound score in an awk script. These score events are then sent to Csound, set to read standard input from the -Lstdin flag, which play the simple FM instrument that I designed.
The simplest way to send stuff to the reciever is to echo to the named pipe (ie echo 'drmfs' > pipe). The sender is an interface for this command. Running the sender command will work, but it doesn't behave the way a shell would (You cannot backspace, for instance.) The program rlwrap acts as a libreadline wrapper for our application, easily providing these niceties.