Shell Process Control

　　If statement

The judging condition is wrapped up in []

If [$a > $b]

Then

Echo ' a > B '

elif [$a < $b]

Then

Echo ' A < b '

Else

Echo ' A==b '

Fi

　　

for Statement

Iterating through an array

For arr in ${array[*]}

Do

Echo ${arr}

Done

while Statement

If the value of the variable is less than 5, then the value of the variable plus 1 output

Var=1

While [$var –lt 5]

Do

var= ' Expr $var +1 '

Echo $var

Done

Defining functions

　　Some functions are reusable, can be encapsulated into functions, the function is defined in the following format:

Function_name () {

List of commands

[Return value]

}

　　Calling functions

The pass-through parameter is optional. If you need to pass a parameter, simply add the argument value after the called function

Function_name 10 20

　　Get the value of a parameter in a function

　　When defining a function, the arguments in parentheses after the function name are not written, to get the parameters passed in the function using $

Get first parameter

$ get second argument

Get the return value of a function

$? is to get the result returned by the previous instruction, then to get the value returned by the function, just write the $ on the line below the statement that called the function.

Shell Process Control