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1.1 root 1: .TH PROC 3
2: .SH NAME
3: proc \- running processes
4: .SH SYNOPSIS
5: .nf
6: .B bind #p /proc
7:
8: .BI /proc/ n /ctl
9: .BI /proc/ n /mem
10: .BI /proc/ n /note
11: .BI /proc/ n /noteid
12: .BI /proc/ n /notepg
13: .BI /proc/ n /proc
14: .BI /proc/ n /segment
15: .BI /proc/ n /status
16: .BI /proc/ n /text
17: .BI /proc/ n /wait
18: \&...
19: .fi
20: .SH DESCRIPTION
21: The
22: .I proc
23: device serves a two-level directory structure.
24: The first level contains numbered directories
25: corresponding to pids of live processes;
26: each such directory contains a set of files
27: representing the corresponding process.
28: .PP
29: The
30: .B mem
31: file contains the current memory image of the process.
32: A read or write at offset
33: .IR o ,
34: which must be a valid virtual address,
35: accesses bytes from address
36: .IR o
37: up to the end of the memory segment containing
38: .IR o .
39: Kernel virtual memory, including the kernel stack for the process and
40: saved user registers (whose addresses are machine-dependent),
41: can be accessed through
42: .BR mem .
43: Writes are permitted only while the process is in the
44: .B Stopped
45: state and only to user addresses or registers.
46: .PP
47: The read-only
48: .B proc
49: file contains the kernel per-process
50: structure.
51: Its main use is to recover the kernel stack and program counter
52: for kernel debugging.
53: .PP
54: The read-only
55: .B segment
56: file contains a textual display of the memory segments
57: attached to the process. Each line has multiple fields:
58: the type of segment (\c
59: .BR Stack ,
60: .BR Text ,
61: .BR Data ,
62: .BR Bss ,
63: etc.); one-letter flags such as
64: .B R
65: for read-only, if any;
66: starting virtual address, in hexadecimal;
67: ending virtual address, and reference count.
68: .PP
69: The read-only
70: .B status
71: file contains a string with eight fields, each followed by a space.
72: The fields are: the process name and user name, each 27 characters left justified;
73: the process state, 11 characters left justified (see
74: .IR ps (1));
75: the six 11-character numbers also held in the process's
76: .B #c/cputime
77: file,
78: and the amount of memory used by the process, except its stack,
79: in units of 1024 bytes.
80: .PP
81: The
82: .B text
83: file is a pseudonym for the file
84: from which the process was executed;
85: its main use is to recover the symbol table of the process.
86: .PP
87: The
88: .B wait
89: file may be read to recover
90: .B Waitmsg
91: records from the exiting children of the process.
92: If the process has no extant children, living or exited,
93: a read of
94: .B wait
95: will block.
96: It is an error for a process to attempt to read its own
97: .B wait
98: file when it has no children.
99: When a process's
100: .B wait
101: file is being read,
102: the process will draw an error
103: if it attempts a
104: .B wait
105: system call; similarly, if a process is in a
106: .B wait
107: system call, its
108: .B wait
109: file cannot be read by any process.
110: .PP
111: Textual messages written to the
112: .B ctl
113: file control the execution of the process.
114: Some require that the process is in a particular state
115: and return an error if it is not.
116: .TP 10n
117: .B stop
118: Suspend execution of the process, putting it in the
119: .B Stopped
120: state.
121: .TP 10n
122: .B start
123: Resume execution of a
124: .B Stopped
125: process.
126: .TP 10n
127: .B waitstop
128: Do not affect the process directly but, like all other messages ending with
129: .BR stop ,
130: block the process writing the
131: .B ctl
132: file until the target process is in the
133: .B Stopped
134: state or exits.
135: Also like other
136: .B stop
137: control messages,
138: if the target process would receive a note while the message is pending,
139: it is instead stopped and the debugging process is resumed.
140: .TP 10n
141: .B startstop
142: Allow a
143: .B Stopped
144: process to resume, and then do a
145: .B waitstop
146: action.
147: .TP 10n
148: .B hang
149: Set a bit in the process so that,
150: when it completes an
151: .IR exec (2)
152: system call, it will enter the
153: .B Stopped
154: state before returning to user mode.
155: This bit is inherited across a
156: .IR fork (2).
157: .TP 10n
158: .B nohang
159: Clear the hang bit.
160: .TP 10n
161: .B kill
162: Kill the process the next time it crosses the user/kernel boundary.
163: .PP
164: Strings written to the
165: .B note
166: file will be posted as a note to the process
167: (see
168: .IR notify (2)).
169: The note should be less than
170: .L ERRLEN-1
171: characters long;
172: the last character is reserved for a terminating NUL character.
173: A read of at least
174: .L ERRLEN
175: characters will retrieve the oldest note posted to the
176: process and prevent its delivery to the process.
177: The
178: .B notepg
179: file is similar, but the note will be delivered to all the
180: processes in the target process's
181: .I note group
182: (see
183: .IR fork (2)).
184: However, if the process doing the write is in the group,
185: it will not receive the note.
186: The
187: .B notepg
188: file is write-only.
189: .PP
190: The textual
191: .B noteid
192: file may be read to recover an integer identifying the note group of the process
193: (see
194: .B RFNOTEG
195: in
196: .IR fork (2)).
197: The file may be written to cause the process to change to another note group,
198: provided the group exists and is owned by the same user.
199: .SH FILES
200: .nf
201: .B /sys/src/9/*/mem.h
202: .B /sys/src/9/*/dat.h
203: .fi
204: .SH SEE ALSO
205: .IR debugger (2),
206: .IR mach (2),
207: .IR cons (3)
208: .SH SOURCE
209: .B /sys/src/9/port/devproc.c
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