Progress of the program and scheduled tasks
One. View and control processes
程序：是保存在外部存储介质（如硬盘、光盘）中的可执行机器代码和数据的静态集合。
进程：是在CPU及内存中处于动态执行状态的计算机程序。
1. Review the process of command
(1)PS命令 ---查看静态的进程统计信息
-a # Show information about all processes currently terminal
-u # use user-based format output
-x # processes the current user information of the terminal at all
-e # all processes within the system information
-l # long format process information
-f # use the full format process information
alone execute ps # displays only the current user session open process
performed, for example: ps -aux
上述信息每段的含义如下：
- USER：启动该进程的用户账号名称
- PID：该进程在系统中的数字ID号
- TTY：表面该进程在哪个终端运行。“？”表示未知或不需要终端
- STAT：显示进程当前状态，S休眠、R运行、Z僵死、<高优先级、N低优先级、s父进程、+前台进程
- START：启动该进程的时间
- TIME：该进程占用的CPU时间
- COMMAND：启动该进程的命令的名称
- %CPU：CPU占用的百分比
- %MEN：内存占用的百分比
- VSZ：占用虚拟内存（swap空间）的大小
- RSS：占用常驻内存（物理内存）的大小
（2）TOP ---查看当前进程动态信息
P # to occupy the CPU by percentage
M # according to the proportion of the sort memory
#kill out process corresponding to K
H help #
q # normal exit top
上述系统任务（Tasks）信息为：
- total：总进程数
- running：正在运行的进程数
- sleeping：休眠的进程数
- stopped：中止的进程数
- zombie：僵死无响应的进程数
- PU占用信息：
- us：用户占用
- sy：内核占用
- ni：优先级调度占用
- id：空闲CPU
- wa：I/O占用
- hi：硬件中断占用
- si：软件中断占用
- st：虚拟化占用
内存占用（Mem）信息：
- total：总内存空间
- userd：已用内存
- free：空闲内存
- buffers：缓冲区域
交换空间（Swap）占用：
- Total：总交换空间
- Used：已用交换空间
- Free：空闲交换空间
- Cached：缓存空间
（3）pgrep ---按条件查询进程
-l # query process name and PID
-U # query a specific user process
-t # query process in particular operation of the terminal
(4) pstree - see the process tree
-p # corresponding PID numbers listed
-u # corresponding list username
-a # complete list of command information
2. Process Control
start up:
“&”操作符： 挂后台
- copy a file to the image file aaa inside, due to the large data, using the "&" linked to the background.
Ctrl + Z # the process of being transferred to the background and execute suspend
bg # will resume suspended tasks run in the background
fg # restore the background to the foreground task
Inquire:
View daemon jobs #
termination:
Ctrl + C # Traps foreground process (common)
the kill PID number # binding process to terminate the process -9 forced termination
killall # terminate multiple processes with the same name -9 forced termination
pkill # terminated in accordance with the process name, user attributes such
-U # specified user
-t # specified terminal,
two. Plan task management
（1）一次性任务设置 ---at
Provided that the atd service system to start
① the current system time to be confirmed by DATE
② set in 16:40 minutes July 13, 2019 of
③ at> tasks performed
④ ctrl + D to submit the task
atq # Query Settings task
atrm # delete the task set
（2）周期性任务设置 ---crontab 前提条件是cron系统服务要启动
-e # edit list of scheduled tasks (the same as the operation vi)
-u # specify the user
-l # list shows scheduled tasks
-r # delete the scheduled tasks list (delete all)
in a nutshell is performed repeatedly:
the format : minutes, hours, days, months, weeks
以上表示在每个月每个星期每天的17：05分执行reboot命令。
- "*" Indicates any time
- "-" indicates a continuous-time range
- "Represents a range of discrete interval"
- "/" Column frequency as the specified interval date field / * represents every 3 days to 3
(3) Note the timing task
is preferably end with a regular scheduled task "> / dev / null 2> & 1" - ">" Redirects
- "/ Dev / null" character special device file, Blackhole equipment or null device
intended to prevent a large number of output log spam.
