The command would be: Code: echo "text" > /dev/ttyUSB0 [code] I am trying to run the above command to test a speech synthesizer. I bought a USB to serial adaptor cable, I have the synthesizer plugged into the adaptor and the adaptor plugged into a USB port on my computer. I was given the above command as a means of testing a speech synthesizer connected through a USB port on my MacBook pro laptop. When I run the command my computer says permission denied. I have read on google about sudo and su. My question is how can I run this command?