I have a large audio project that involves a lot of separate Audacity files stored in multiple subdirectories within one master directory.
Is there a command I can run that can go through all the files, and give me a total time in minutes and seconds for the length of all the files combined?
What do you mean by “Audacity files”?
Audacity “projects” have two parts, a “project file” (with a .AUP file extension) and (separately) the audio data.
A basic understanding of what a “project” is, is very important. You can read about it here: Audacity Manual
For “projects” there’s no easy way to get an exact duration without opening the project.
For a project that contains just one stereo track with the default sample rate of 44100 Hz, then you can approximate the length by dividing the size of the project “_data” folder (in MB) by 20. That will give you the approximate length in minutes.
For example, if the project data folder is 600 MB, an it contains one stereo track at 44100 Hz sample rate, then the length is probably around 30 minutes.
Note that there are many things that can make this approximation wildly out, for example, gaps in a track require very little data.
Note also that this only applies to saved, closed projects - an open project can have much more data due to “Undo” data.