Nice book, and very approachable. The little details covered in the first two chapters are still pretty relevant (and fun to play with). The hints at principles underlying the system design choices are what I found most interesting. They talk about composability (pipes, fd redirection) and how UNIX builds on the notion of breaking down distinctions that separate data. By choosing not to put up safety rails and limits on access you leave the door open to creative use and new ideas.

I was disappointed to see on my machine (Debian, Linux 5.9.0-1-amd64):

Quote:universal rule in UNIX ... anywhere you can use ordinary filename, you can use a pathname

They mention a 14 character limit on filenames, but don't go into why exactly ...
These days ext2, ext3, ext4 filesystems all allow 255 byte names.

They talk about nohup and how it automatically calls nice ...
Seems this isn't true anymore, at least in gnu coreutils: "This command does not change the niceness (i.e. the priority) of a command."

Trivia:

Quote:^ is an obsolete synonym for the pipe