Loop statement in Shell, instance of Judgment statement _linux Shell

There are 3 main types of shell loops, for,while,until
The Shell's branch judgment is mainly 2 kinds, if,case

A, for loop

Copy Code code as follows:

#!/bin/bash

For file in $ (ls/tmp/test/mytest |grep SH) The//for in format is the basic format for the shell for, and the root JS for in is similar
Do//cycle start you take it as {
Echo $file
Done//Loop end you think of it as}

For ((i=0;i<10;i++))//note is double parenthesis, due to the influence of other languages, it is easy to mistake
Todo
Echo-n $i
Done

echo \//Output line Wrap

For i in 0 1 2 3 4 5 6 7 8 9
Todo
Echo-n $i
Done

echo \

For-I in "0 1 2 3 4 5 6 7 8 9"//This root is a different one, this loop only loops once, double quotes inside is just a variable
Todo
Echo-n $i
Done

Exit 0

Two, while loops

Copy Code code as follows:

#!/bin/bash
I=0
while ((I<10))
Todo
Echo $i
((i + 1))
Done

I=0
While [$i-LT 10]//Note the space on the two sides of the bracket
Todo
Echo $i
Let "i+=1"//+ 1
Done
Exit 0

Three, until cycle

Copy Code code as follows:

#!/bin/bash

End_condition=end
Until ["$var 1" = "$END _condition"]//Read the variable root set variables equal to exit the loop, otherwise forever loop
Todo
echo "Input variable #1"
echo "($END _condition to exit)"
Read Var1
echo "Variable #1 = $var 1"
Echo
Done
Exit 0

Four, if statement

Copy code code as follows:

#!/bin/bash

echo "Input a number #1"
Read num
echo "Variable #1 = $num"

If [$num-lt 60]//Note the front of Lt--it's easy to forget
Then
echo "You are not are"
elif [$num-lt] && [$num-ge 60]//judgment of multiple conditions
Then
echo "Pass"
elif [[$num-lt && $num-ge 70]]//If put together, be aware that both brackets are not written [$num-lt && $num-ge 70]
Then
echo "Good"
Elif (($num <=)) && (($num >= 85))//For people who have a language base, this kind of writing is very comfortable, don't forget the double parenthesis
Then
echo "Very good"
Else
echo "num is wrong"
Fi//if to have the end tag, the root XML is very similar, not closed, the error

Exit 0

Five, Case statement

Copy Code code as follows:

#!/bin/sh
Case is in
Start
echo "Start OK"
;; Note that a double semicolon should be noted
Stop
echo "Stop OK"
;;
Restart)
echo "Restart OK"
;;
*)
echo "No param"
;;
ESAC//Note closing label
Exit 0

[root@krlcgcms01 forif]# sh c1.sh stop
Stop OK