PROC(3) PROC(3) NAME proc - running processes SYNOPSIS bind #p /proc /proc/n/args /proc/n/ctl /proc/n/fd /proc/n/fpregs /proc/n/kregs /proc/n/mem /proc/n/note /proc/n/noteid /proc/n/notepg /proc/n/ns /proc/n/proc /proc/n/profile /proc/n/regs /proc/n/segment /proc/n/status /proc/n/text /proc/n/wait ... 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 pro- cess. 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 files regs, fpregs, and kregs hold representations of the user-level registers, floating-point registers, and ker- nel registers in machine-dependent form. The kregs file is read-only. Page 1 Plan 9 (printed 12/25/24) PROC(3) PROC(3) The read-only fd file lists the open file descriptors of the process. The first line of the file is its current direc- tory; subsequent lines list, one per line, the open files, giving the decimal file descriptor number; whether the file is open for read (r), write, (w), or both (rw); the type, device number, and qid of the file; its I/O offset; and its name at the time it was opened. The read-only ns file contains a textual representation of the process's file name space, in the format of namespace(6) accepted by newns (see auth(2)). The last line of the file identifies the current working directory of the process, in the form of a cd command (see rc(1)). The information in this file is based on the names files had when the name space was assembled, so the names it contains may be inac- cessible if the files have been subsequently renamed or rearranged. The read-only segment file contains a textual display of the memory segments attached to the process. Each line has mul- tiple fields: the type of segment (Stack, Text, Data, Bss, etc.); one-letter flags such as R for read-only, if any; starting virtual address, in hexadecimal; ending virtual address, and reference count. The read-only status file contains a string with twelve 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 (see ps(1)) - the six 11-character numbers also held in the process's #c/cputime file - the amount of memory used by the process, except its stack, in units of 1024 bytes - the base and current scheduling priority, each 11 char- acter numbers The read-only args file contains the arguments of the pro- gram when it was created by exec(2). If the program was not created by exec, such as by fork(2), its args file will be empty. The format of the file is a list of quoted strings suitable for tokenize; see getfields(2). 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. Page 2 Plan 9 (printed 12/25/24) PROC(3) PROC(3) The wait file may be read to recover Waitmsg records from the exiting children of the process. If the process has no extant children, living or exited, a read of wait will block. It is an error for a process to attempt to read its own wait file when it has no children. When a process's wait file is being read, the process will draw an error if it attempts a wait system call; similarly, if a process is in a wait system call, its wait file cannot be read by any process. Textual messages written to the ctl file control the execu- tion of the process. Some require 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 com- pletes an exec(2) system call, it will enter the Stopped state before returning to user mode. This bit is inherited across a fork(2). closefiles Close all open file descriptors in the process. nohang Clear the hang bit. kill Kill the process the next time it crosses the user/kernel boundary. pri n Set the base priority for the process to the inte- ger n. wire n Wire the process to processor n. The priority is interpreted by Plan 9's multilevel process scheduler. Priorities run from 0 to 19, with higher numbers representing higher priorities. A process has a base Page 3 Plan 9 (printed 12/25/24) PROC(3) PROC(3) priority and a running priority which is less than or equal to the base priority. As a process uses up more of its allocated time, its priority is lowered. Unless explicitly set, user processes have base priority 10, kernel processes 13. Children inherit the parent's base priority. The read-only profile file contains the instruction fre- quency count information used for multiprocess profiling; see tprof in prof(1). The information is gleaned by sampling the program's user-level program counter at interrupt time. 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 pro- cess 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)). However, if the process doing the write is in the group, it will not receive the note. The notepg file is write-only. The textual noteid file may be read to recover an integer identifying the note group of the process (see RFNOTEG in fork(2)). The file may be written to cause the process to change to another note group, provided the group exists and is owned by the same user. FILES /sys/src/9/*/mem.h /sys/src/9/*/dat.h SEE ALSO debugger(2), mach(2), cons(3) SOURCE /sys/src/9/port/devproc.c Page 4 Plan 9 (printed 12/25/24)