These Unix archive (ar) files contain the source code from "Software Tools", by Brian Kernighan and P. J. Plauger, published by Addison-Wesley in 1976. As one might expect, they are mostly of historical interest, although the book is still in print and selling, albeit not rapidly.
If you have trouble cracking the archive format, toolstape is the whole thing as one big ASCII text file, as it was distributed on the 9-track tape that was sold for a while.
You are welcome to make whatever use you can of them, subject to the fact that they are copyrighted by Bell Labs. If you do find a use, we would appreciate acknowledgement of the original source of the material.
No warranties, etc., etc. -- this is old code indeed.