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stay shell Script , When some commands or operations need to be used frequently , It's too cumbersome to rewrite every time , Then we can use the function , When needed , Just call the function directly .

One . Function basic format

Function, write some command sequences together in format , It is convenient to reuse the command sequence
Function definition format ：

Method 1 ：
function Function name {
      Command sequence
      return x  # Show end of function
}
Method 2 ：
Function name （）{
  Command sequence
}

Function call ： Function name [ Parameters 1][ Parameters 2]

Two . Function call

2.1 Call in function

Call the current function directly in the function

2.2 Function call function

When defining a function , Other functions can also be called inside

2.3 External call

The function's role is in its modularity , Convenient for next use , Call directly to use . So every time we write a script , You can call the previously written function directly , Just make a declaration before use .

2.4 Case study

Use functions to configure local yum Source warehouse

3、 ... and . summary

1. function ： Encapsulated reusable code with characteristic functions , It is a bit similar to the command alias
2. Functions can be called directly in functions , It can also be called outside the function ,
3. When calling externally, you must first declare the called function
4. For functions with the same name , Only the last defined function is recognized