procfs
also: proc filesystem, /proc
A virtual filesystem (/proc) that provides a window into kernel data structures and running processes, allowing users and programs to read process information and kernel statistics as if they were regular files.
procfs (proc filesystem) is a special filesystem mounted at /proc that doesn't store data on disk. Instead, it dynamically generates file contents on-the-fly by reading kernel memory, making process and system information accessible through standard file operations.
Each running process gets its own directory under /proc named by its PID (Process ID). For example, /proc/1234/ contains files like cmdline (the command that started the process), status (memory usage, state, etc.), and maps (memory mappings). You can inspect them with cat /proc/1234/status.
System-wide information lives directly in /proc, such as /proc/cpuinfo (CPU details), /proc/meminfo (memory statistics), and /proc/uptime (system uptime). Many Linux tools like ps, top, and free read from procfs to gather their data.