Shell Program Design-Functions

Shell programming-functions-general Linux technology-Linux programming and kernel information. For more information, see the following. Function is indispensable for developing a large shell program. It can reuse code with high degree, simplify development, modularization, and strong team cooperation.
Function Definition Format:
Functionname ()
{
Statement Group
}
Function usage:
1. Before calling a function, you must define the function.
2. function parameter transfer: functionname para1 para2 ....
3. Read parameters in the function: $ * $ @ $ #$1 $2 $3 $4 $5...
$0 is not included. The $0 parameter can be referenced inside the function. Therefore, the program parameters cannot be referenced within the function. After the function is executed, these values are restored.
4. function return value: the return command may be used to return the numeric value. To return the string value, you can store the string in a global variable, which can be used by the outside world after the function is completed; if the return command is not used, the return value of the function is the exit status code of the Last Command executed in the function.
5. Use variables: the variables declared in the function are global variables by default, and the variables declared using the local keyword are local variables (such as local var = "var "). If the local variable has the same name as the global variable, the local variable inside the function overwrites the global variable.
6. Obtain the return value. After the function is executed, the return value of the function is stored in $? To obtain the return value of the function.
#! /Bin/sh
# This is a example for testing the return value of function
Fun ()
{
Return 10
}
Fun
Echo $?
Exit 0