NAME

proc − running processes

SYNOPSIS

­bind #p /proc
 /proc/n/ctl
/proc/n/mem
/proc/n/note
/proc/n/notepg
/proc/n/proc
/proc/n/segment
/proc/n/status
/proc/n/text
...

DESCRIPTION

The ­proc device serves a two-level directory structure.  The first level contains numbered directories corresponding to pids of live processes; each such directory contains a set of files representing the corresponding process. 

The ­mem file contains the current memory image of the process.  A read or write at offset ­o, which must be a valid virtual address, accesses bytes from address o up to the end of the memory segment containing ­o.  Kernel virtual memory, including the kernel stack for the process and saved user registers (whose addresses are machine-dependent), can be accessed through mem.  Writes are permitted only while the process is in the ­Stopped state and only to user addresses or registers. 

The read-only ­proc file contains the kernel per-process structure.  Its main use is to recover the kernel stack and program counter for kernel debugging. 

The read-only ­status file contains a string with eight fields, each followed by a space.  The fields are: the process name and user name, each 27 characters left justified; the process state, 11 characters left justified; the six 11-character numbers also held in the process’s ­#c/cputime file, and the amount of memory used by the process, except its stack, in units of 1024 bytes. 

The ­text file is a pseudonym for the file from which the process was executed; its main use is to recover the symbol table of the process. 

Textual messages written to the ­ctl file control the execution of the process.  Some presume that the process is in a particular state and return an error if it is not. 

­stop Suspend execution of the process, putting it in the ­Stopped state. 

­start Resume execution of a ­Stopped process. 

­waitstop Do not affect the process directly but, like all other messages ending with stop, block the process writing the ­ctl file until the target process is in the ­Stopped state or exits.  Also like other ­stop control messages, if the target process would receive a note while the message is pending, it is instead stopped and the debugging process is resumed. 

­startstop
Allow a ­Stopped process to resume, and then do a ­waitstop action. 

­hang Set a bit in the process so that, when it completes an exec(2) system call, it will enter the ­Stopped state before returning to user mode.  This bit is inherited across a fork(2).

­kill Kill the process with extreme prejudice. 

Strings written to the ­note file will be posted as a note to the process (see notify(2)). The note should be less than ­ERRLEN-1 characters long; the last character is reserved for a terminating NUL character.  A read of at least ­ERRLEN characters will retrieve the oldest note posted to the process and prevent its delivery to the process.  The ­notepg file is similar, but the note will be delivered to all the processes in the target process’s ­note group (see fork(2)). The ­notepg file is write-only. 

FILES

­/sys/src/9/∗/mem.h
­/sys/src/9/∗/dat.h

SEE ALSO

cons(3)

Plan 9  —  January 03, 1993