for loop 备忘

for Loop:

Syntax:

for {variable name} in {list}

do

  #do statements untill varibles are out of list

  {statements/commands}

done

e.g. 1:

[fedora@novice shell_scripts]$ cat > testfor.sh

for i in 1 2 3 4 5

do 

   echo "welcome $i time(s)"   

done

[fedora@novice shell_scripts]$ sh testfor.sh

welcome 1 time(s)

welcome 2 time(s)

welcome 3 time(s)

welcome 4 time(s)

welcome 5 time(s)

Another syntax:

for ((expr1;expr2;expr3))

do

  {statements/commands}

  #do statements or commands when expr2 is true

done

e.g. 2:

[fedora@novice shell_scripts]$ cat >testfor1.sh

for ((i=0;i<=5;i++))

do

   echo "Welcome $i time(s)"      

done

[fedora@novice shell_scripts]$ sh testfor1.sh

Welcome 0 time(s)

Welcome 1 time(s)

Welcome 2 time(s)

Welcome 3 time(s)

Welcome 4 time(s)

Welcome 5 time(s)

nested for loop:

e.g.3:

#!/bin/bash

#

#test nested for loop

#

for ((i=1;i<=5;i++))

do

   for((j=1;j<=5;j++))

   do

      echo -n "$i"

   done

   echo ""

done

[fedora@novice shell_scripts]$ sh nestedfor.sh 

11111

22222

33333

44444

55555

e.g. 4:

打印九九乘法表

#!/bin/bash 

#

#print chengfabiao

#

for ((i=1;i<=9;i++))

do

   for ((j=1;j<=i;j++))

   do

      echo -n "$j * $i =`expr $i \* $j` "

   done

   echo ""

done

[fedora@novice shell_scripts]$ sh jiujiu.sh 

1 * 1 =1 

1 * 2 =2 2 * 2 =4 

1 * 3 =3 2 * 3 =6 3 * 3 =9 

1 * 4 =4 2 * 4 =8 3 * 4 =12 4 * 4 =16 

1 * 5 =5 2 * 5 =10 3 * 5 =15 4 * 5 =20 5 * 5 =25 

1 * 6 =6 2 * 6 =12 3 * 6 =18 4 * 6 =24 5 * 6 =30 6 * 6 =36 

1 * 7 =7 2 * 7 =14 3 * 7 =21 4 * 7 =28 5 * 7 =35 6 * 7 =42 7 * 7 =49 

1 * 8 =8 2 * 8 =16 3 * 8 =24 4 * 8 =32 5 * 8 =40 6 * 8 =48 7 * 8 =56 8 * 8 =64 

1 * 9 =9 2 * 9 =18 3 * 9 =27 4 * 9 =36 5 * 9 =45 6 * 9 =54 7 * 9 =63 8 * 9 =72 9 * 9 =81 

下面还提供了一些练习，有兴趣的可以看看：