Shell script – loop

October 18, 2021By Simo Unix

1. The writing method of for statement based on C language format:

for((i=0;i<10;i++)); do【for (initial conditions ; Conditional judgment statement; Value change statement); do】

　　 loop body

done

The advantage of for loop: it is not easy to enter an infinite loop

2, the format of the while statement:

initial value

While condition; do

　　 loop body

　　Let i++ (change the initial value)

Done

Exercise: write a for loop to traverse all up computers in this network segment

 #!/bin/bash 
 
 declare -i sum =0 
 for i in $( seq 1 100); do 
   /code> ping -c 1 -w 1 10.6.12.$i &> /dev/null 
   if< /code> [ $? - eq 0 ]; the n 
   let sum ++ 
   echo "10.6.12.$i是通的" 
   else 

 < code class="bash spaces">  echo "10.6.12.$i is not working" 
   fi 
 done 
 echo "There are a total of $sum computers online" 
 

Find the even sum of 1-100

#!/bin/bash

for i in $( seq 0 2 100); do

let sum +=$i


   echo $i 

 done 
 echo  $ sum

Print the nine-nine multiplication table

< div class="line number2 index1 alt1"> 2

< div class="container">

for i in {1..9}; do

for ((j=1 ;j<=$i;j++)); do


  echo -n -e " $i*$j=$(($i*$j))\t" 

    done 

   echo 

 done

< /div> 












#!/bin/bash

declare -i sum =0

for i < code class="bash keyword">in $( seq 1 100); do

ping -c 1 -w 1 10.6.12.$i &> /dev/null


   if [ $? - eq 0 ]; then 

   let sum code> ++ 

   echo "10.6.12.$i是通的" 

  else 

   else 

   /code> echo "10.6.12.$i is not working"


   fi 

 done 
 echo  "There are a total of $sum computers online"

#! /bin/bash

declare


 code> -i sum =0


 for i in< /code> $( seq 1 100); do 

   ping -c 1 -w 1 10.6.12.$i &> /dev/null 

   if [ $? - eq 0 ];  then 

   let sum ++ 

   echo "10.6.12.$i是通的" 
  else 

  echo "10.6.12.$i is not working" 

 < div class="line number11 index10 alt2">   fi 
 done 

 echo "There are a total of $sum computers online"

1< /p>

#!/bin/bash

declare -i sum =0

for i in $( seq 1 100); do

/code> ping -c 1 -w 1 10.6.12.$i &> /dev/null


  if [ $? - eq 0 ]; then 

   let sum ++ 

    echo < code class="bash string">"10.6.12.$i是通的" 
    else 

   echo "10.6.12.$i is not working" 

   fi 

 done 
 echo " in total $sum computers online" 

#!/bin/bash

 p>
declare -i sum =0
for i in $( seq  1 100); do
 ping -c 1 -w 1 10.6.12.$i &> /dev /null
 if [ $? - eq 0 ]; then

 let sum < code class="bash plain">++
  echo "10.6.12.$i是通的"

 else
  echo " 10.6.12. $i is not working"
 fi
 p>

done
echo "A total of $sum computers are online"





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 #!/bin/bash 
  
 for i in $( seq code> 0 2 100); do 
 < code class="bash spaces"> let sum + =$i 
   echo < code class="bash plain">$i 
 done 
 echo $ sum  









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 #!/bin/bash 
 
 for i in < code class="bash plain">$( seq 0 2 100); do 
    let code> sum +=$i 

  echo $i 

 done 
 echo $ sum 





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6< /p>
7
 #!/bin/bash 
 < div class="line number2 index1 alt1">


 for i< /code> in $( seq 0 2 100); do 

   let sum +=$i 
   echo $i 

 done 
 echo $ sum 

#!/bin/bash

for < code class="bash plain">i in $( seq 0 2 100); do
  let sum +=$i< /code>

 echo $i code>
done
echo $ sum





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 for i in {1..9}; do 
   for ((j=1;j<=$i;j++)); do 
   echo -n -e "$i*$j=$(($i*$j))\ t" 

    done  
   echo 

 done 










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 < code class="bash keyword">for i in  {1..9}; do 
   /code> for ((j=1;j<=$i;j++)); do 

    echo code> -n -e "$i*$j=$(($i*$j))\t" 

   done 

   echo 

 done 





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 for i in {1..9};  do 
     for   ((j=1;j<=$i;j ++));  do 
                    echo   -n -e   "$i*$j=$(($i*$j))\t" 
            done 
            echo 
  done 

for  i  in  {1..9}; do
         for  ((j=1;j<=$i;j++)); d o
                 echo  -n -e  "$i*$j=$(($i*$j))\t"
         done
         echo
done

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