Shell script (5)-function format, parameter passing, variables, recursion, function library

One, shell function definition

• Write the command sequence together in a format to facilitate repeated use of the command sequence

Two, format

1. Format 1:

function 函数名 {
    
    

命令序列

}

2. Format 2:

函数名() {
    
    

命令序列

}

Three, function return value

• return means to exit the function and return an exit value, which can be displayed by the $? variable in the script

• Principle of use:

  • 1. Take the return value as soon as the function ends, because the $? variable only returns the exit status code of the last command executed
  • 2. The exit status code must be 0~255, and the value will be divided by 256 when it is exceeded.

Four, function parameter transfer

Five, the scope of function variables

• Functions in Shell scripts are only valid in the current Shell environment
• Variables in Shell scripts are globally effective by default
• Use the local command to limit the variable to the function

Six, recursion

1. Factorial

2. Recursive search directory

Seven, create a function library

Put commonly used functions into a separate library script, so that when the script is in use, you can directly call the functions in this library