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for loop In practical work, we often encounter the situation that a task needs to be executed multiple times, and each time it is executed, only the processing objects are different and other commands are the same. For example, create a system account according to the name list in the address book, and check the survival status of each h ...

10.1 what is a shell (1) What is Shell Shell is the medium used when the system interacts with computer hardware. It is just a tool of the systemIn fact, there is another layer between the system and computer hardware - the system kernel (1_1) record command historyThe commands we have executed in Linux will be recorded. By default, 1000 hist ...

1.Shell condition test 1.1. Numerical comparison: Operator: gt: greater thanlt: less thaneq: equal tone: not equal toge: greater than or equal tole: less than or equal to Test syntax: Mode 1: test conditional expression [root@VM-0-17-centos ~]# test 8 -ge 2 / / no value is returned when the command is executed directly [root@VM-0 ...

I Array definition method Method 1 Array name= (value0 value1 value2 ...) Method 2 Array name=([0] =value [1]=value [2]=value ... ) Method 3 List name="value0 value1 value2 ..." Array name=($List name) Method 4 Array name[0]="value" Array name[1]="value" Array name[2]="value" ☝ matters needing attention: Ⅰ. Data types ...

1. Functions What is a function? A function is a block of function code that can be used many times, a closed (space), and can be called freely in the code. Encapsulation of functions can reduce duplicate code development and improve code utilization. Functions can be passed along, using pre-defined content within the function to process ...

catalogue 1, shell function 1.1. Definition of function (1) Format of function (2) Function return value 1.2. Function call 1.3.return 1.4. Parameter passing of function 1.5. Scope of function 1.6. Local and global variables 1.7. Case of function Factorial Build local warehouse 2, Array 2.1. Definition of array 2.2. Array represe ...

Linux learning linux Process Process concept From the perspective of users: a process is a running program. From the perspective of operating system: when the operating system runs a program, it is necessary to describe the running process of the program through a structural task_struct {}, collectively referred to as PCB, so for the oper ...

1, Regular expression overview linux text processing tool Text processorBasic regular expressionExtended regular expressionvi editorsupportgrepsupportegrepsupportsupportsedsupportawksupportsupport 1. Basic regular expression Metacharactereffect\Escape character, used to cancel the meaning of special symbols^Start position of matching str ...

1.inotify+rsync If you want to synchronize data regularly, you can add rsync to the scheduled task at the client, but the synchronization time granularity of the scheduled task can not meet the requirements of real-time synchronization. Inotify file system monitoring mechanism is provided after Linux kernel 2.6.13. Real time synchronization ca ...

Shell script is a sharp tool to help programmers and system administrators complete time-consuming and laborious boring work. It is an effective way to interact with computers and manage file and system operations. Just a few lines of code can make the computer close to acting according to your intention. Brother Tian sorted out 100 examples f ...