Controlling processes via the /proc filesystem

Implemented by the Process Manager component of procnto, the /proc virtual filesystem lets you access and control every process and thread running within the system.

The /proc filesystem manifests each process currently running on the system as a directory whose name is the numerical process ID (in decimal) of the process. Inside this directory, you'll find the following files:

as

The address space that contains the process's entire memory space.

cmdline

The arguments passed to the process, separated by null characters. For example:

# pidin -p 28687 arg
      pid Arguments
    28687 io-pkt-v6-hc -dsmsc9500 mac=96a414016206
# echo `cat /proc/28687/cmdline`
io-pkt-v6-hc-dsmsc9500mac=96a414016206

exefile

The path of the executable file used to run the process. For example:

# echo `cat /proc/28687/exefile`
/sbin/io-pkt-v6-hc

Threads are accessible through the as file created for the process; you can select a thread via devctl() calls. You can use the following standard functions to access the /proc filesystem:

Function	Purpose
open()	Establish a file descriptor to a process
read()	Read data from the process's address space
write()	Write data to the process's address space
stat()	Return struct stat information
lseek()	Establish a position within the process's address space for further operations
devctl()	Manipulate a process or thread
close()	Release a file descriptor

Ancillary functions (such as readdir(), opendir(), and so on) are supported on the directory /proc itself—this aids in implementing commands such as ls.