Overview
The ps (English spelling: process status) command is used to display the status of the current process, similar to the Windows Task Manager
You can use the kill command to interrupt and delete unnecessary programs at any time.
Syntax and parameters
ps [options] [--help]
Common parameters
- -A lists all processes
- -w display widening can display more information
- -au displays more detailed information
- -aux displays all processes containing other users
- -f displays UID, PID, PPIP, C, STIME, STIME, TTY, TIME, CMD fields
- -a: Displays programs executed under all terminals, except the stage job leader.
- a: Display all programs under the current terminal, including programs of other users.
- -e: The effect of this option is the same as specifying the "A" option.
- e: When listing programs, display the environment variables used by each program.
au(x) output format (column description)
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
Column description
USER: trip owner,用户名UIDThe program is owned by this UIDPID:进程ID（Process ID）PPID·It is its上级父程序的ID%CPU: occupied CPU usage,进程的cpu占用率%MEM: Memory usage occupied by the process内存占用率VSZ: The size of virtual memory occupied,进程所使用的虚存的大小（Virtual Size）RSS: The size of memory occupied, the size of the resident set used by the process, or实际内存的大小，Kbytes字节TTY: Minor device number of tty,与进程关联的终端（tty）STAT: The status of this trip:- D: Uninterruptible sleep state (usually IO process)
- R: Executing
- S: stationary state
- T: pause execution
- Z: Does not exist but cannot be eliminated temporarily
- W: Not enough memory pages available to allocate
- <: High priority itinerary
- N: low priority itinerary
- L: There are memory pages allocated and locked in the memory (real-time system or A I/O)
START: trip start time,进程启动时间和日期TIME: Execution timeCOMMAND:Instruction executed
Usage examples
root:# ps aux
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
smmsp 3521 0.0 0.7 6556 1616 ? Ss 20:40 0:00 sendmail: Queue runner@01:00:00 f
root 3532 0.0 0.2 2428 452 ? Ss 20:40 0:00 gpm -m /dev/input/mice -t imps2
htt 3563 0.0 0.0 2956 196 ? Ss 20:41 0:00 /usr/sbin/htt -retryonerror 0
htt 3564 0.0 1.7 29460 3704 ? Sl 20:41 0:00 htt_server -nodaemon
root 3574 0.0 0.4 5236 992 ? Ss 20:41 0:00 crond
xfs 3617 0.0 1.3 13572 2804 ? Ss 20:41 0:00 xfs -droppriv -daemon
root 3627 0.0 0.2 3448 552 ? SNs 20:41 0:00 anacron -s
root 3636 0.0 0.1 2304 420 ? Ss 20:41 0:00 /usr/sbin/atd
dbus 3655 0.0 0.5 13840 1084 ? Ssl 20:41 0:00 dbus-daemon-1 --system
Display all processes and output to the specified file
Display all processes and output to ps001.txt file
ps -aux > ps001.txt
View the specified process
ps -ef # 显示所有进程信息，连同命令行
ps -ef | grep ssh # ps 与grep 常用组合用法，查找特定进程
UID、PID、PPIP、C、STIME、STIME、TTY 、TIME、 CMD
# ps -ef | grep php
root 794 1 0 2020 ? 00:00:52 php-fpm: master process (/etc/php/7.3/fpm/php-fpm.conf)
www-data 951 794 0 2020 ? 00:24:15 php-fpm: pool www
www-data 953 794 0 2020 ? 00:24:14 php-fpm: pool www
www-data 954 794 0 2020 ? 00:24:29 php-fpm: pool www
...
Display specified user information
ps -u root //显示root进程用户信息
kill process
The kill command sends the specified signal to the corresponding process. Not specifying a model will send SIGTERM (15) to terminate the specified process.
The kill command can take the signal number option or not. If there is no signal number, the kill command will issue a termination signal (15). This signal can be captured by the process, allowing the process to clean up and release resources before exiting.
# 杀死进程：kill pid
kill 12345
# 强制杀死进程 kill -KILL pid
kill -KILL 123456
# 彻底杀死进程：kill -9 pid
kill -9 123456
The kill command of Linux sends a signal to the process. Kill does not mean to kill. -9 means to exit unconditionally, but it is up to the process to decide whether to exit. This is why kill -9 cannot terminate system processes and daemon processes.