scmuser created the topic: Nested for loop in Linux Shell Script
As you see the if statement can nested, similarly loop statement can be nested. You can nest the for loop. To understand the nesting of for loop see the following shell script.
$ vi nestedfor.sh
for (( i = 1; i <= 5; i++ )) ### Outer for loop ###
do
for (( j = 1 ; j <= 5; j++ )) ### Inner for loop ###
do
echo -n "$i "
done
echo "" #### print the new line ###
done
Run the above script as follows:
$ chmod +x nestedfor.sh
$ ./nestefor.sh
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
Here, for each value of i the inner loop is cycled through 5 times, with the varible j taking values from 1 to 5. The inner for loop terminates when the value of j exceeds 5, and the outer loop terminets when the value of i exceeds 5.
Following script is quite intresting, it prints the chess board on screen.
$ vi chessboard
for (( i = 1; i <= 9; i++ )) ### Outer for loop ###
do
for (( j = 1 ; j <= 9; j++ )) ### Inner for loop ###
do
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
Run the above script as follows:
$ chmod +x chessboard
$ ./chessboard
Above shell script cab be explained as follows:
I’m Rajesh Kumar, a DevOps, SRE, DevSecOps, Cloud, and Platform Engineering expert passionate about sharing practical knowledge, real-world experiences, and industry best practices. I have worked at Cotocus and regularly write about technology, travel, investing, health, product reviews, and digital marketing through my various platforms.
I publish technical articles at DevOps School, travel stories at Holiday Landmark, stock market insights at Stocks Mantra, health and fitness guidance at My Medic Plus, product reviews at TrueReviewNow, and SEO and digital marketing strategies at Wizbrand.
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