My mistake- it was always dev/com7, not usb 7. Here's the error in full:
Error inside Serial.()
gnu.io.PortInUseException: Unknown Application
at gnu.io.CommPortIdentifier.open(CommPortIdentifier.java:354)
at processing.app.Serial.(Serial.java:127)
at processing.app.Serial.(Serial.java:72)
at processing.app.Uploader.uisp(Uploader.java:156)
at processing.app.Uploader.uploadUsingPreferences(Uploader.java:78)
at processing.app.Sketch.upload(Sketch.java:1693)
at processing.app.Sketch.exportApplet(Sketch.java:1755)
at processing.app.Editor$40.run(Editor.java:1892)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
Error: Permission denied
-> /dev/com7
I've tried exiting programs that might try and grab the same port, but I've had no luck so far. >:(