Starting from learning shell

Start from shell-general Linux technology-Linux programming and kernel information. For more information, see the following. I just learned shell. Make a draft!
SHELL value comparison expression
Eq equal to ge greater than or equal to le less than or equal to ne not equal to gt greater than lt less
Word expression
= Equal! = Not equal
SHELL numeric operation
Expr number + number
$ (Number + number ))
SHELL comparison statement
If
If test $ var
Then .....
Else
.....
Fi
-----------------------------------
If []


SHELL statement
For
For var in list
Do
......
Done
-------------------------------------
While
While cond
Do
....
Done


Until
Until cond
Do
....
Done

The difference between while and unile is that while is executed when the condition is met, while unile is executed when the condition is not met.

SHELL branch statement
If cond1 then
....
Elif cond2 then
....
Elif cond3 then
....
....
Else
....
Fi
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Case
Case string in
Str1 | str2)
...
Str3 | str4)
...;;
Str5 | str6)
...;;
*)
...;;
Esac
Echo "usage: inetpanel [start | begin | commence | stop | end | destory | restart | again]"
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Select name [in word;] do list; done