Shell---case, for, while

Case section:

#!/bin/bash                                 //program starts #file:  case.shecho  "==========" echo  "welcome!" echo  "1 copy" echo  "2 delete" echo  "3 backup" echo  "4 Quit" echo  "= = = ======= "echo " Please input your select: "read n                //Read input case  $n  in                1)   echo  "Your select  is copy! "     ;;     2)   echo  "your select is delete!"    ;;     3)   echo  "your select is backup!"    ;;     4)   echo  "your select is quit!"     ;;     *)   echo  "your select is invalid!"   ;; esac                                         //Program End

For section:

#!/bin/bash//program start #file:for.shfor N in 1 2 3 4 5//Turn N to loop assignment do echo ' The number is: $n ' done End of program

While section:

Print the square value of a natural number less than 10

#!/bin/bash//program start #file:while.shn=1while [$n-lt 10]//As long as n is less than 10 execute do squ= ' expr $n \* $n ' The N squared echo $squ//Output square value n= ' expr $n + 1 '//n gradually add 1 to match 10done//program knot Beam

The power value of print 2 is less than 100

#!/bin/bash//program start #file:var.shn=1while ["$n"-lt "] do echo" The value is: $n "N= ' ex PR $n \* 2 ' done//end of program

Print half a positive triangle

#!/bin/bash                    //program starts #file: interactive.shread -p  "Please input a number:"  num        //reads the number of rows entered read -p  "Please input a  charsymbol: " sym    //read into the displayed symbols a=1while [  $a  -le  $num  ]           //Outer Loop, A is less than or equal to the number of rows entered do             b=1                        //b represents the number of symbols printed              while [  $b  -le  $a  ]             //the number of symbols printed is less than or equal to the number of lines              do                         echo -n  "$sym"         //-n means no line break, print symbols                          b= ' expr  $b  + 1 '     // The number of symbols continues to increase to match a               done              echo              //= NewLine              a= ' expr  $a  + 1 '          // A constant increase to match the number of rows done                           //Program End 

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The next half inverted triangle, positive triangle, the windmill continues to update!

This article from "Experience from pain" blog, declined reprint!

Shell---case, for, while