ps(1) — Linux manual page
NAME
ps - report a snapshot of the current processes.
SYNOPSIS
ps [options]
DESCRIPTION
ps displays information about a selection of the active processes. If you want a repetitive update of the selection and the displayed information, use top(1) instead.
This version of ps accepts several kinds of options:
1、UNIX options, which may be grouped and must be preceded by a dash.
2、BSD options, which may be grouped and must not be used with a dash.
3、GNU long options, which are preceded by two dashes.
NOTE: 显然
ps的实现，根据dash个数来区分是哪种option。结合后文来看，1UNIX option是standard。
Options of different types may be freely mixed, but conflicts can appear. There are some synonymous（同义的） options, which are functionally identical, due to the many standards and ps implementations that this ps is compatible with.
Note that "ps -aux" is distinct from "ps aux". The POSIX and UNIX standards require that "ps -aux" print all processes owned by a user named "x", as well as printing all processes that would be selected by the -a option. If the user named "x" does not exist, this ps may interpret the command as "ps aux" instead and print a warning. This behavior is intended to aid in transitioning(过渡) old scripts and habits. It is fragile, subject to change, and thus should not be relied upon.
By default, ps selects all processes with the same effective user ID (euid=EUID) as the current user and associated with the same terminal as the invoker. It displays the process ID (pid=PID), the terminal associated with the process (tname=TTY), the cumulated(累计的) CPU time in [dd-]hh:mm:ss format (time=TIME), and the executable name (ucmd=CMD). Output is unsorted by default.
[tensorflow@localhost ~]$ ps
PID TTY TIME CMD
1741 pts/0 00:00:00 bash
2109 pts/0 00:00:00 ps
The use of BSD-style options will add process state (stat=STAT) to the default display and show the command args (args=COMMAND) instead of the executable name. You can override this with the PS_FORMAT environment variable. The use of BSD-style options will also change the process selection to include processes on other terminals (TTYs) that are owned by you; alternately, this may be described as setting the selection to be the set of all processes filtered to exclude processes owned by other users or not on a terminal. These effects are not considered when options are described as being "identical" below, so -M will be considered identical to Z and so on.
Except as described below, process selection options are additive. The default selection is discarded, and then the selected processes are added to the set of processes to be displayed. A process will thus be shown if it meets any of the given selection criteria.
Examples
All process
To see every process on the system using standard syntax:
ps -e
ps -ef
ps -eF
ps -ely
To see every process on the system using BSD syntax:
ps ax
ps axu
Process tree
To print a process tree:
ps -ejH
ps axjf
Threads
To get info about threads:
ps -eLf
ps axms
Security info
To get security info:
ps -eo euser,ruser,suser,fuser,f,comm,label
ps axZ
ps -eM
Run as root
To see every process running as root (real & effective ID) in user format:
ps -U root -u root u
User-defined format
To see every process with a user-defined format:
ps -eo pid,tid,class,rtprio,ni,pri,psr,pcpu,stat,wchan:14,comm
ps axo stat,euid,ruid,tty,tpgid,sess,pgrp,ppid,pid,pcpu,comm
ps -eopid,tt,user,fname,tmout,f,wchan
Process ID of
Print only the process IDs of syslogd:
ps -C syslogd -o pid=
Name of
Print only the name of PID 42:
ps -p 42 -o comm=
ps -x
Process Selection
NOTE: 使用
ps的一个非常重要的内容是：process selection
Simple Process Selection
Process Selection By List
These options accept a single argument in the form of a blank-separated or comma-separated list. They can be used multiple times. For example: ps -p "1 2" -p 3,4
-C cmdlist
Select by command name.
This selects the processes whose executable name is given in cmdlist.
-G grplist
Select by real group ID (RGID) or name.
This selects the processes whose real group name or ID is in the grplist list. The real group ID identifies the group of the user who created the process, see getgid(2).
Output Format Control
These options are used to choose the information displayed by ps. The output may differ by personality.
-F
extra full format. See the -f option, which -F implies.
-O format
Notes
This ps works by reading the virtual files in /proc. This ps does not need to be setuid kmem or have any privileges to run. Do not give this ps any special permissions.
NOTE: 参见
Programming\Process\Proc-filesystem。
This ps needs access to namelist data for proper WCHAN display. For kernels prior to 2.6, the System.map file must be installed.
NOTE
wikipedia System.map
CPU usage
CPU usage is currently expressed as the percentage of time spent running during the entire lifetime of a process. This is not ideal, and it does not conform to the standards that ps otherwise conforms to. CPU usage is unlikely to add up to exactly 100%.
SIZE and RSS
The SIZE and RSS fields don't count some parts of a process including the page tables, kernel stack, struct thread_info, and struct task_struct. This is usually at least 20 KiB of memory that is always resident. SIZE is the virtual size of the process (code+data+stack).
<defunct>
Processes marked <defunct> are dead processes (so-called "zombies") that remain because their parent has not destroyed them properly. These processes will be destroyed by init(8) if the parent process exits.
If the length of the username is greater than the length of the display column, the numeric user ID is displayed instead.
System.map file
This ps needs access to namelist data for proper WCHAN display. For kernels prior to 2.6, the System.map file must be installed.
NOTE:
本段所描述的问题，在stackoverflow in ps -l, what does wchan=stext mean? 中也对这个问题进行了探讨。
关于
System.mapfile，参见Kernel\Guide\Debug\System.map。
Process Flags
The sum of these values is displayed in the "F" column, which is provided by the flags output specifier.
- 1 forked but didn't exec
- 4 used super-user privileges
NOTE: 没有理解意思
Process State Codes
NOTE: Process State 非常重要
Here are the different values that the s, stat and state output specifiers (header "STAT" or "S") will display to describe the state of a process.
D
Uninterruptible sleep (usually IO)
NOTE: docstore 21.7. Hanging Processes: Detection and Diagnostics 中，有这样的描述:
'
D' disk wait inpsreport所以，我觉得
D应该代表的就是disk wait。
I
Idle kernel thread
R
Running or runnable (on run queue)
S
Interruptible sleep (waiting for an event to complete)
T
Stopped, either by a job control signal or because it is being traced.
W
paging (not valid since the 2.6.xx kernel)
X
dead (should never be seen)
Z
Defunct ("zombie") process, terminated but not reaped by its parent.
For BSD formats and when the stat keyword is used, additional characters may be displayed:
<
high-priority (not nice to other users)
N
low-priority (nice to other users)
L
has pages locked into memory (for real-time and custom IO)
NOTE: 关于此，参见:
s
is a session leader
l
is multi-threaded (using CLONE_THREAD, like NPTL pthreads do)
+
is in the foreground process group
Examples
In UNIX, what are the Ss, Sl, and Ssl proccess types I see with ps aux?
From the ps manpage:
S Interruptible sleep (waiting for an event to complete) For BSD formats and when the stat keyword is used, additional characters may be displayed: s is a session leader l is multi-threaded (using CLONE_THREAD, like NPTL pthreads do)