Shell function application

1. Definition of Shell function

1 Write the command sequence format together to facilitate repeated use of the command sequence.

2 Function return value:

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

• Usage principles:
  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 if it exceeds .

• Note: The returned value 0-255 uses $? carried out.

• Format 1:
  function function name { command sequence }
  
  
  
  

• Format 2:
  function name () { command sequence }
  
  
  
  

2. Function parameter transfer

• The parameters of the position variable are passed to the script.
  
  

3. 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
  
  

Four. Recursion

• The function calls its own function.
  
  

Five. Create a library