Suppose, you create a script that does N automated tasks. However, you want to create it in such a way, that it runs 1 to N number of tasks, depending on one of the CLI argument (decimal equivalent of binary number of N digits).
Scenario
Let us take N=3, so the decimal equivalent of min-max binary numbers would be 0 and 7. So, assuming the automated tasks are A, B, C. So, here’s binary notation for A, B, C and their equivalent decimal numbers.
A B C 0 0 0 = 0 0 0 1 = 1 0 1 0 = 2 0 1 1 = 3 1 0 0 = 4 1 0 1 = 5 1 1 0 = 6 1 1 1 = 7
So, in the above tabular data, ONE denotes that task A should run, whereas ZERO denotes that the tasks shouldn’t run. For instance, FIVE denotes that A and C will run.
# BNRY_CMB contains the value obtained from CLI argument..
flag=$BNRY_CMB
# Start infinite loop..
while :;
do
case $BNRY_CMB in
1) # Run Task 'A'
case $flag in
1|3|5|7) break;;
esac
;;
2|3) # Run Task 'B'
case $flag in
2|6) break;;
3|7) BNRY_CMB=1; continue;;
esac
;;
4|5|6|7) # Run Task 'C'
case $flag in
4) break;;
5) BNRY_CMB=1; continue;;
6|7) BNRY_CMB=2; continue;;
esac
;;
esac
done
Smartly, making use of case-esac construct and infinite loop, you can handle all the automated tasks (A and/or B and/or C). Well, this scenario helped me understand the basics of case-esac and while-loop constructs, easily.
Hope this helps 😉
PrayogShala 