Process and planned task management

• Process and plan task management outline
  • 1. Basic concepts
    • Program
    • process
      • Father child process
    • Threads
      • Single thread
  • 2. static state / Dynamic statistics of process and system load
    • 1.ps
    • 2. top
    • 3.jobs( Including some background operations )
    • 4.pstree
    • 5.pgrep
    • 6. Terminate the process
  • 3. Periodic tasks
• Basic concepts （ Program process Threads ）

  

  • 1. Program
    • The definition of program ： Executable code or data stored on CD or hard disk , It's a static concept , Only load the program into memory , The system can only execute after allocating resources for it , This state of execution is called process
  • 2. process
    • Process definition ： A process is a process of dynamic execution of a program , A program can create multiple processes , Complete tasks by consuming system resources , Is the basic unit of resources allocated by the operating system , Most processes are independent of each other , Each process has its own independent address space , Processes can create threads to complete more refined operations , Processes are safer than threads , If the process fails, it should be independent of each other and will not affect , And thread failure ,os When feedback to the process is detected , There may be something wrong .
    • The concept of parent-child process ： The parent process affects the child process , There is a relationship between them , The child process is logically derived from the parent process , If the parent process exits , And one or more of its subprocesses is still running , These processes are called orphan processes , The orphan process will be init Process adoption , And by the init The process completes the status collection for it . If the child process exits the parent process and is too busy to withdraw the child process, a zombie process will occur , The zombie process is essentially dead, so you can't kill it , You need to kill its parent process to kill it
  • 3. Threads
    • Definition of thread ： A thread is an instance in a process , Relying on the process , Shared process space address ,cpu Resources, etc , It should be that threads are not independent of each other, so a thread problem may affect all threads
    • Single thread concept ： Single core and single thread can only execute one task at a time , When the task volume is large, it will cause congestion ,CPU At the micro level, the time to process threads is very short , It's called a time slice , In theory CPU Deal with tasks one by one , You can complete multithreaded tasks at your own speed .
• static state / Dynamic statistics of process and system load （ps jobs top pgrep pstree）
  • 1.ps（ View static process statistics ）
    • ps -aux：（ Briefly display the information of all processes in the system ）（aux The detailed content  ）

      

      • -u： Output process information in user oriented format
      • -x： Display the output process information in user oriented format
      • -a： Display the information of all processes under the current terminal , Including other processes
    • ps -elf：( Display system process information in long format )（elf The detailed content ）

      

      • -e： Display all process information in the system
      • -l： Use long format to display process information
      • -f： Display process information in full format
  • 2. top（ Dynamically view the status of the process and the load of the system ）

    

    • 1.（15:51:20 up 3:41） Time of the system now System process running time
    • 2.（2 user） Two users
    • 3.（load average：0.0 0.01 0.05）CPU Average load value A minute Five minutes 15 Average load in minutes
    • 4.（Tasks） How many tasks are there
    • 5.（running） There are several running
    • 6.（sleeping） There are several ready
    • 7.（stopped） There are several stops
    • 8.（zombie） There are several zombie processes
    • 9. Using a digital 1 You can see all cpu The proportion of
      • 1. us: user cpu Proportion
      • 2.sy: System cpu Proportion
      • 3.ni: Priority scheduling occupies
      • 4.id: Free cpu
      • 5.wa:I/O Waiting for occupation
      • 6.hi: System interrupt occupancy
      • 7.si: Software interrupt occupancy
      • 8.st: Virtualization takes up
  • 3.jobs（ View background processes ）
    • 1.jobs -l（ View all processes in the background and display pid）

      

    • ######（ Some scattered knowledge points about the backstage ）######
    • ctrl + z： Pause the current process and suspend in the background
    • &： Added at the end of the order , Indicates that the command is run in the background
    • fg： Turn the suspended background to the foreground to start
    • bg： Keep the process suspended in the background starting in the background
    • nohup xxxx &： Run the program in the background , However, closing the terminal does not affect the operation of the program
  • 4.pstree（ List process information in a tree structure ）

    

    • pstree -pua
      • -p： When using this option, you can list the corresponding PID Number
      • -u： Option to list the corresponding user names
      • -a： Select to list the complete commands
  • 5.pgrep（ Query process information ）
    • pgrep -l： Query the process with the specified name , And show their PID Number

      

    • pgrep-u： Query the specified user PID Number

      

    • pgrep-t： Query the processes allowed on a specific terminal
  • 6. Terminate the process （Kill ,killall,pkill）
    • 1.kill（ Terminate the process adopt PID Number ）
      • kill xxxx（PID Number ） Terminate the process
      • kil -9 xxxx（PID Number ） Force process termination
    • 2.killall（ End process by process name ）
      • killall xxxx（ The name of the process ） Terminate the process with the specified process name
      • killall -9 xxxx（ Process name ） Forcibly terminate the process with the specified process name
    • 3.pkill（ Through the user to which the process belongs -u Or terminal -l The end of the process ）
      • pkill -9 -u “ xxxx”（ end xxxx The user's process ）
      • pkill-9 -i “xxxxx”（ end xxxx The process of the terminal ）
• Planning task management （at and crontab）
  • One time task setup

    

    • at [HH:MM] [yyyy-mm-dd]
    • Finally using ctrl+d end
  • Periodic task setup
  • crontab Schedule tasks through multiple directories and files , Different types of tasks are set by different configuration files
    • -e : Manually add recurring tasks

      

    • If you want to start some tasks automatically, you need to enter the configuration file to modify

      

    • -r: Delete configured recurring tasks
• a key
  • Understand the concept of process thread , adopt Top Check the process , Observe for one minute, ten minutes 15 Minute load trend , Analyze the cause of the failure
  • Skillfully use ,ptree（ The tree displays process information ）,pgrep（ Specify a name / User query process ）,jobs（ View background processes ）,ps（ Static view process ）
  • Understand process termination Kill, How to exit gracefully
  • Set up scheduled tasks , Single task at And periodic tasks crontab, understand * * * * * , Setting of time sharing day, month and week
• difficulty
   
  • ps/top SATAT Process type , Processing of the value of system load , And the commands of each query process , Format compilation of periodic tasks
• Summary of notes
  • This chapter mainly understands the commands for viewing system process information （ps-elf ps-aux）, And specify to view user processes （pgrep -u） And through the pgrep- i and kill The specified termination process is carried out in the form of combination , Set periodic tasks , Complete regular functions
• Use Technology Association links
   
  • Linux Under the crontab Execute the task command regularly | 《Linux It's time to learn 》【crontab】
  • http://t.csdn.cn/LdpCF【loadaverage analysis 】