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ps-进程状态管理.md

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ps command

Linux is a multitasking, multi-user operating system, so it allows multiple processes to run simultaneously without interfering with each other. Process is one of the important basic concepts of the Linux operating system. A process is an instance of a program that performs different tasks in the operating system. Linux provides us with a utility called ps to view information related to processes on the system. It is an abbreviation for process status. The ps command is used to list the currently running processes, their pid, and some other information depending on different options. It reads process information from virtual files in the /proc file system. process status command ps displays information about active processes, similar to the Task Manager in Windows. Each operating system's version of ps is slightly different, so if detailed information is needed, it is necessary to consult the operating system's wiki.

Syntax

ps [options]

Parameters

The ps command has various categories of parameters to choose from: simple|list|output|threads|misc|all.

Simple Process Selection

  • -A, -e: Select all processes.
  • -a: Select all processes except session leaders and processes without a controlling terminal.
  • a: List all processes with a terminal tty, including processes from other users, or list all processes when used with the x option.
  • -d: Select all processes except session leaders.
  • -N, --deselect: Select all processes except those that satisfy the specified conditions.
  • r: Restrict the selection to only running processes.
  • T: Select all processes associated with this terminal.
  • x: List processes without controlling terminals for a pseudoterminal, just like ps and EUID, or list all processes when used with the a option.

Process Selection By List

  • -C <command>: Select by command name, this selects processes whose executable name is given in command.
  • -G, --Group <GID>: Select by real group ID (RGID) or name, this selects processes with a real group name or ID in the grplist.
  • -g, --group <group>: Select by session or effective group name.
  • -p, p, --pid <PID>: Select by process ID.
  • --ppid <PID>: Select by parent process ID, this selects processes with a parent process ID from the pidlist, in other words, it selects the child processes of those processes listed in pidlist.
  • -q, q, --quick-pid <PID>: Select by process ID (quick mode).
  • -s, --sid <session>: Select by session ID.
  • -t, t, --tty <tty>: Select by tty (terminal).
  • -u, U, --user <UID>: Select by effective user ID (EUID) or name.
  • -U, --User <UID>: Select by real user ID (RUID) or name.

Output Format Control

  • -F: Extra full format.
  • -f: Full format listing, this option may be combined with other UNIX style options to add additional columns, it also causes the command arguments to be printed. When used with -L, it will add the NLWP thread count and LWP thread ID columns.
  • f, --forest: ASCII art process hierarchy, like many trees, also called a forest.
  • -H: Display process hierarchy (forest).
  • -j: Job control format.
  • j: BSD job control format.
  • -l: Long format, the -y option is often useful with this.
  • l: Display BSD long format.
  • -M, Z: Add a security data column for SE Linux.
  • -O <format>: Preload default column list.
  • O <format>: Similar to -O with BSD features.
  • -o, o, --format <format>: Specify user-defined format.
  • s: Display signal format.
  • u: Display user-oriented format.
  • v: Display virtual memory format.
  • X: Display register format.
  • -y: Do not show flags, display rss instead of addr, this option can only be used with -l.
  • --context: Display security context format when using SE Linux.
  • --headers: Repeat the header line, printing it on each page of output.
  • --no-headers: Do not print the header line at all.
  • --cols, --columns, --width <num>: Set screen width.
  • --rows, --lines <num>: Set screen height.

Thread Display

  • H: Show threads as if they were processes.
  • -L: Display threads, possibly with LWP and NLWP columns.
  • -m, m: Show threads after processes.
  • -T: Display threads, possibly with SPID column.

Miscellaneous options

  • -c: Display different scheduler information for -l option.
  • c: Display the actual command name.
  • e: Show environment after command.
  • k, --sort: Specify sorting order as [+|-]key[,[+|-]key[,...]].
  • L: Display format flags.
  • n: Show numeric uid and wchan.
  • S, --cumulative: Include some dead child process data.
  • -y: Do not display flags, show rss, only used with -l.
  • -V, V, --version: Display version information.
  • -w, w: Unlimited output width.
  • --help <simple|list|output|threads|misc|all>: Display help information.

Examples

Display processes for the current shell.

ps

View all running processes.

ps -e

Usually, viewing all processes can be combined with pipe and grep to filter, for example, we can view all processes related to nginx.

ps -e | grep nginx

View all processes except session leaders and processes not associated with a terminal.

ps -a

View all processes for the www user.

ps -u www

View all processes for the www group.

ps -G www

Use -f to view the complete format list.

ps -f

View processes in a user-defined format.

ps -aN --format cmd,pid,user,ppid

Sort processes by memory usage.

ps -eo pid,ppid,cmd,%mem,%cpu --sort=-%mem

Display all current processes, for ease of viewing, it can be used in combination with pipe and less command.

ps -ax | less

Use the aux parameter, add CPU and memory usage information to display comprehensive information.

ps -aux | less

Sort processes in descending order by CPU usage.

ps -aux --sort -pcpu | less

Sort processes in descending order by memory usage.

ps -aux --sort -pmem | less

Sort processes based on overall memory and CPU usage and display only the top 10 results.

ps -aux --sort -pcpu,+pmem | head -n 10

Question of the Day

https://github.com/WindrunnerMax/EveryDay

References

https://www.computerhope.com/unix/ups.htm
https://www.runoob.com/linux/linux-comm-ps.html
https://www.geeksforgeeks.org/ps-command-in-linux-with-examples/