Programming :: Using A Variable To Control A BASH For Loop

I know of 4 different ways to use a for loop:

1. for I in {1..10}; do echo $I; done|

2. for I in 1 2 3 4 5 6 7 8 9 10; do echo $I; done|

3. for I in $(seq 1 10); do echo $I; done|

4. for ((I=1; I <= 10 ; I++)); do echo $I; done

I have a script which uses the 1st form of for loop. I'm trying to modify it to use a variable instead of a static hard-coded value in the section that controls the looping.of the for loop.

I've tried all different ways of quoting and escaping the variable, and the problem is that the quoting chars and escape char are being translated and passed into the loop along with the value stored in the variable.

For example, to change the start value of 1 to whatever value I want passed in through a variable:

Change:

I have tried: {{$a}..10} and {`$a`..10}, to have the variable evaluated first.

I have tried using the eval() function.

I have tried single and double quotes and the backslash escape character.

Nothing I've tried works. It's probably a syntax error.