Procfs

On information about processes. Because /proc is not a real file system, it does not consume any storage space, and it consumes only a limited amount of memory.

The filesystem is often mounted at /proc. It is supported under Solaris Operating Environment, Berkeley Software Distribution and Linux, and the latter also extends it to non-process-related data.

=History=

The UNIX 8th Edition version of /proc was implemented by Tom J. Killian, who presented a paper titled Processes as Files at USENIX in June 1984. It was designed in order to replace the ptrace system call used for process tracing.

Roger Faulkner and Ron Gomes ported V8 /proc to System V Release 4, and published a paper called The Process File System and Process Model in UNIX System V at USENIX in January 1991. This kind of procfs supported the creation of ps (Unix), but the files could only be access with functions read(), write(), and ioctl().

4.4BSD implemented /proc with subdirectories for each process, and the ability to access memory, registers, and current status. Solaris 2.6 /proc (finished in 1996) also had separate directory for each process, as well as a special ctl file which allowed for control, tracing and manipulation of processes.

=Linux=

Under Linux, /proc provides information on any running process at /proc/ PID , but in addition to that it also includes:

*A symbolic link to the current (traversing) process at /proc/self *Information on hardware, kernel, and module configuration *Access to dynamically-configurable kernel options under /proc/sys

The basic utilities that use /proc under Linux are in the procps package, and they require that /proc is mounted in order to function.

In kernel 2.6, much of the non-process related files under /proc were moved to a separate pseudo-filesystem called sysfs (mounted under /sys).