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This article mainly explains "the usage of the Linux basic command ps". The content of the article is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "the usage of the Linux basic command ps".

Ps

The ps instruction can display information about the current process in the system, and its output is highly customizable. If you want to update the selection and displayed information repeatedly, use top (1) instead.

Note that "ps-aux" is different from "ps aux". The POSIX and UNIX standards require "ps-aux" to print all processes owned by a user named "x" and all processes selected by the-an option. If a user named "x" does not exist, this ps can interpret the command as "ps aux" and print a warning. This behavior is designed to help convert old scripts and habits. It is fragile and can change at any time, so it should not be relied on.

By default, ps selects all processes with the same valid user ID (EUID=EUID) as the current user and the terminal associated with the caller. It displays the process ID (PID=PID), the terminal associated with the process (tname=TTY), the cumulative CPU time (time=TIME) in [dd-] hh:mm:SS format, and the executable name (ucmd=CMD). The output is not sorted by default.

Using the BSD style option adds the process status (stat=STAT) to the default display and displays the command args (args= command) instead of the executable name. You can override this operation using the PS_FORMAT environment variable. Using the BSD-style option also changes the process selection to include processes on other terminals (TTY) that you own, or this can be described as a collection of all processes that the selection is set to filter to exclude processes owned by other users or processes on the terminal. When the option is described as "the same", these effects are not taken into account, so-M will be considered the same as Z, and so on.

The scope of this command: RedHat, RHEL, Ubuntu, CentOS, SUSE, openSUSE, Fedora.

1. Grammar

Ps [options]

2. List of options

Option

Description

-- help

Show help documentation

-V | V |-- version

Show command version

-- info

Display debugging information

L

List all formats

Simple option

-A |-e

Select all processes

-N |-- deselect

Reverse selection does not meet the criteria

T

Select the terminal that matches

-a

Select all processes except session processes and terminal-independent processes.

A

This option causes ps to list all processes with terminals (TTY), or all processes when used with the x option.

-d

Select all processes and ignore the process owner

G

All processes, including session leadership

R

Limit the selection to run only the process.

X

This option causes ps to list all the processes you own (the same EUID as ps), or to list all processes when used with the an option.

Multiple option

These options accept individual parameters in a blank-separated or comma-separated list. They can be used many times.

-Ccmdlist

Select by command name. This selects the process that gives the executable name in the cmdlist.

-Ggrplist

Select the process to which the group id that the process belongs to matches the given list

Uuserlist

Select by valid user ID (EUID) or name. Valid user ID describes the user whose file access permissions are used by the process

-Uuserlist

Select by actual user ID (RUID) or name. The real user ID identifies the user who created the process

-ggrplist

Select by session or valid group name.

P pidlist

Select by process ID.

-ppidlist

Select by process ID.

-ssesslist

Select according to session ID

T ttylist

Select via tty. Almost the same as-t and-- tty, but can also be used with an empty ttylist to indicate the terminal associated with the ps.

-t ttylist

Select the specified tty

-uuserlist

Select by valid user ID (EUID) or name, which is equivalent to "U and"-- user "

-- Groupgrplist

Equivalent to "- G"

-- Useruserlist

Equivalent to "- U"

-- groupgrplist

Select by valid group ID (EGID) or name. Valid group ID describes the group for which the process uses its file access permissions.

-- pidpidlist

Equivalent to "- p" and "p"

-ppidppidlist

Select the id matching process of the parent process

-- sidsesslist

Equivalent to "- s"

-- ttyttylist

Equivalent to "- t" and "t"

-- useruserlist

Equivalent to "- u" and "U"

-123

Equivalent to "--sid 123"

one hundred and twenty three

Equivalent to "- pid 123"

3. Output format control

Format

Description

-f |-F

Output the complete format. It also causes command parameters to be output. When used with-L, the NLWP (number of threads) and LWP (thread ID) columns are added.

-Oformat

Similar to-o, but preloaded with some default columns. Equivalent to "- o pid,format,state,tname,time,command" or "- o pid,format,tname,time,cmd"

Oformat

Preloaded o. When used as a formatting option, it is exactly the same as-O and has a BSD personality.

-M

Add a list of security data.

X

Register format

Z

Equivalent to "- M"

-c

Displays different scheduler information for the-l option.

J

BSD job control format

-j

Job format

L

BSD long format

-l

Long format, often used with "- y"

Oformat

Equivalent to "- o" and "--format"

-oformat

User-defined format. Format is a single parameter in the form of a space-separated or comma-separated list that provides a way to specify a single output column. The header can be renamed as needed (ps-o pid,ruser=RealUser-o comm=Command). If all column headings are ps-o pid=-o comm=, the header row will not be output. The column width required for wide headers will increase; this can be used to extend columns such as WCHAN (ps-o pid,wchan=WIDE-WCHAN-COLUMN-o comm). Explicit width control (ps opid,wchan:42,cmd) is also provided. The behavior of ps-o pid=X,comm=Y varies with personality, and the output may be a column named "XGraincommuy" or two columns named "X" and "Y". Use the PS_FORMAT environment variable to specify default values as needed; DefSysV and DefBSD are macros that can be used to select default UNIX or BSD columns.

S

Display signal format

U

User-oriented mode

V

Virtual memory-based mode

-y

Do not display flag bits

-Z

Show security context format

-- formatformat

Same as "- o"

-- context

Show security context format

4. Output modifier

Modifier

Description

-H

Show process hierarchy

O order

Sorting, outdated operation

S

Summarize some information, such as CPU usage, from dead child process to parent process.

C

Displays the real command name. This is derived from the name of the executable file, not from the argv value. Therefore, the command parameters and any modifications to them are not displayed

E

Display the environment after the command

F |-- forest

Process hierarchy in ASCII format

H

No head.

K spec

Specify the sort order, equivalent to "--sort"

-nnamelist | N namelist

Proper WCHAN display requires a name list file and must exactly match the current Linux kernel to get the correct output. If this option is not available, the default search path for the name list is:

$PS_SYSMAP

$PS_SYSTEM_MAP

/ proc/*/wchan

/ boot/System.map- `uname-r`

/ boot/System.map

/ lib/modules/ `uname-r` / System.map

/ usr/src/linux/System.map

/ System.map

N

Digital output of WCHAN and User. (including all types of UID and GID)

-w | w

Wide output, use this option twice for infinite width

-- cols n |-- columns n |-- width n

Set the screen width

-- cumulative

Includes some dead child process data (as the sum of the parent process)

-- headers

Repeat the header line to output one line per page

-- no-headers

The title line is not printed at all

-- lines n |-- rows n

Set the screen height

-- sort spec

Sort. The syntax is "[+ | -] key [, [+ | -] key [,...]], for example, ps jax-- sort=uid,-ppid,+pid

5. Thread mode

Thread mode

Description

H

Display threads as processes

-L

Display the LWP NLWP of the thread

-T

Display the SPID of the thread

M |-m

Display threads after a process

6. Description

This ps works by reading the virtual file in "/ proc". This ps does not need to be a setuid kmem, nor does it require any privileges to run. Do not give this ps any special permissions. This ps requires access to the name list data to get the correct WCHAN display. For kernels prior to 2.6, the System.map file must be installed.

CPU usage is currently expressed as the percentage of time that the process has been running throughout the lifecycle. CPU usage is unlikely to reach 100%.

The SIZE and RSS fields do not calculate parts of the process, including page tables, kernel stacks, structures thread_info, and task_struct. This is usually at least the memory size of 20kb. SIZE is the virtual size of the process (code data stack).

Processes marked "defunct" are dead processes (so-called "zombies") because their parent process did not destroy them correctly. If the parent process exits, init (8) destroys those processes.

If the length of the user name is greater than the length of the display column, the digital user ID is displayed.

7. Process flag

The sum of these values is displayed in the F column, which is provided by the flag output specifier.

1, already fork, but not executed.

4, use superuser privileges.

8. Process status code

Here are the different values that the s, stat, and state output specifiers (header "stat" or "S") will display to describe the state of the process:

D, uninterrupted sleep (usually IO).

R, running or runnable (on the run queue).

S, can interrupt sleep (wait for the event to complete).

T, stop, either blocked by the job control signal, or because it is being tracked.

W, paging (invalid since the 2.6.xx kernel).

X, dead (should not be seen).

Z, stopped ("zombie") process, terminated but not harvested by its parent process.

For bsd format and when using the stat keyword, additional characters may be displayed:

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