Shell Script Tutorial

Logic - FOR

Example 1 :

for i in 1 2 3 4 5; do echo "Welcome $i times" done

Resuit:
Welcome 1 times
Welcome 2 times
Welcome 3 times
Welcome 4 times
Welcome 5 times


Example 2 :

for i in `cat /tmp/shadow`; do id=`echo $i | cut -d ':' -f1,1` echo "" echo "[$id] password is changed" echo -e "123456\n123456\n" | passwd $id done

This scripts is used to changed password for mass linux account.


Example 3 :

for (( i = 0; i <= 5; i++ )); do echo "Welcome $i times" done

Resuit:
Welcome 1 times
Welcome 2 times
Welcome 3 times
Welcome 4 times
Welcome 5 times


Example 4:

for (( i = 1; i <= 5; i++ )); do ### Outer for loop ### for (( j = 1 ; j <= 5; j++ )); do ### Inner for loop ### echo -n "$i " done echo "" #### print the new line for break ### done

This is nesting of FOR loop, Resuit:
1 1 1 1 1
2 2 2 2 2
3 3 3 3 3
4 4 4 4 4
5 5 5 5 5


Example 5:

for (( i = 1; i <= 9; i++ )); do ### Outer for loop ### for (( j = 1 ; j <= 9; j++ )); do ### Inner for loop ### tot=`expr $i + $j` tmp=`expr $tot % 2` if [ $tmp -eq 0 ]; then echo -e -n "\033[47m " else echo -e -n "\033[40m " fi done echo -e -n "\033[40m" #### set back background colour to black echo "" #### print the new line ### done

This chess-board will be printed with this nesting of FOR loop.


Example 6:

f1="/tmp/word1.txt" f2="/tmp/word2.txt" for i in `cat $f1`; do for j in `cat $f2`; do if [ $i = $j ]; then echo $i fi done done

This script is designed to get the same word/line compare between with 2 files.




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