01-22-2012
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Join Date: Dec 2007
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Indeed. Hopefully, not everything is a file under Unix. What is true is that many OS objects that aren't files on other operating systems, like devices (printers, disks, partitions, network interfaces, serial lines, ...), processes, virtual and physical memory, sockets, named pipes and the likes are files present in most Unix file systems hierarchies.
However, plenty of other OS objects, like partition tables, signals, threads, queues, statistics and others have no direct file equivalent.
In any case, as far as the operating system is concerned, a user (id) is just one of the many properties a process has.