Content structure:
View the process
Process control
at a one-time task settings
crontab periodic task set
(A) view the process
Relations programs and processes
program
In the hard disk, an optical disk medium such as executable code and data
Static code saved
process
Program code running in memory and cpu
Dynamic code execution
Parent and the child
Each process can create one or more processes
Thread
A process contains multiple threads
Process is a collection of threads
View static process statistics -ps command,
[Root @ localhost ~] # ps aux simple form display process information
a: View all the current process system
u: Specifies the user
x: The user process at all terminals (TTY) in ps / 0 remote terminal
[Root @ localhost ~] #ps -elf long display format information system processes
e: All
f: complete form
l: long form
View the dynamic processes ranking information -top (refresh once every three seconds)
Depending on the particular conditions of the query process PID command information -pgrep
[Root @ localhost /] # pgrep -l "log" to view details of the current user log-related processes
[Root @ localhost /] # pgrep -l -U test1 "bash" to view detailed information about the specified user process
Process information in a tree structure lists the command -pstree
[Root @ localhost /] # pstree -aup user to view the current process of tree
a: Show full information
u: list of usernames
p: PID number corresponding to the list
[Root @ localhost /] # pstree -ap test1 test1 user to view the properties of the specified process
(B) control process
Manual start
Reception Start: user input commands directly execute the program
Start backstage: Add the "&" symbol at the end of the command line
Front and back of the scheduling process
Key combinations Ctrl + z
The current process is suspended and transferred to the background and stop execution
jobs command
View is in the background of the Task Manager (-l show details)
fg command
The recovery background process to the foreground, you can specify job numbers
bg command
Will resume a process running in the background and run
Ctrl + c key combination
Interrupt command being executed
kill，killall命令
kill PID to terminate the specified number of processes
killall用于终止指定名称的所有进程
-9选项用于强制终止
pkill命令
根据特定条件终止相应的进程
常用选项
-U：根据进程所属用户名终止相应进程
-t：根据进程所在的终端终止相应进程
（三）at 一次性计划任务设置
at命令
at [HH：MM] [yyyy-mm-dd] 小时：分钟 年-月-日
atq 查看当前系统计划任务
atrm 删除计划任务
Ctrl+d 提交任务
（四）crontab 周期性计划任务设置
crontab命令
安装预先设置的时间周期（分，时，日，月，周）重复执行用户指定的命令操作
属于周期性计划任务
主要设置文件
全局配置文件/etc/crontab
系统默认的设置/etc/cron.*/
用户定义的设置/var/spool/cron/用户名
管理cron计划任务
编辑计划任务
crontab -e [-u 用户名]
查看计划任务
crontab -l [-u 用户名]
删除计划任务
crontab -r [-u 用户名]