If I have a file with name "read7" with a list of numbers in it, for example:
2
3
4
How can I write a bash script with a while loop to read all the elements in the file and square the numbers and send it as a standard output?
So, after running the script we should get an output of
4
9
16
If you want to use a while loop, you could say:
while read -r i; do echo $((i*i)); done < read7
For your input, it'd emit:
4
9
16
As per your comment, if the file has words and numbers in it. How do I make it read just the numbers from the file?. You could say:
while read -r i; do [[ $i == [0-9]* ]] && echo $((i*i)); done < read7
For an input file containing:
2
foo
3
4
it'd produce:
4
9
16
Try awk:
awk '{print $1*$1}' read7
You don't need to use while loop. Using awk:
$ cat read7
2
3
4
$ awk '{print $1*$1}' read7
4
9
16
