Linux’s /proc filesystem is one of the stranger ideas in Unix — a directory that doesn’t exist on disk, populated entirely by the kernel at runtime with files that represent live system state. Want the memory map of a running process? It’s a file. CPU info? A file. Currently mounted filesystems, open file descriptors, network statistics, kernel parameters? Files, all of them. The conceit is elegant: everything is a file, including the guts of the operating system itself. /proc was borrowed from Plan 9 and landed in Linux in 1991. It later spawned /sys, which took over hardware-related entries when /proc became embarrassingly cluttered. Neither is a real filesystem. Both are navigable with ls and cat. Sysadmins have been reading kernel internals with text tools ever since, which is either Unix philosophy triumphant or a sign that something has gone profoundly sideways.
