Shell Programming and Scripting

Hello,

I am struggling with using variable made using "eval".

Code:

a=4
eval b$a=20

echo $b$a ??? [does not work]

As shown above, I am trying to call back the variable "bX" assuming I do not know the value of "a".

How can I do that?
I tried several combinations but nothing worked.

Thanks

Hi.

The name of your new variable is b + the value of a:

Code:

$ a=4
$ eval b$a=20

$ echo $b4   
20

To this point I knew it.

The problem is that I want to use it blindly:

Code:

k=1
while [ $k -le 10 ]
do
  eval zo${k}=`awk -v k=$k {my_script} my_file`
  echo $zo${k} -> That does not work
  k=`expr $k + 1`
done

How should I change the "echo" part?

By using "eval echo ..."?

I could not get anything working...

Hi.

I'm somewhat confused now as to what you're actually trying to achieve.

Code:

$ eval echo b$a
b4

Stop using backticks, and stop using the completely annoying expr commands.

Code:

k=$((k + 1))

Looking at your code, it looks like the eval is not the problem.

What is this all about?:

Code:

eval zo${k}=`awk -v k=$k {my_script} my_file`

I am trying to define several variables using an awk script. The awk part will parse "my_file" make some operation, and return a single value.

For each different value of "k", the awk script will return a different value I want to store in different variables. I wish I could use a matrix, but just don't know if that's possible with bash.
Thus, I am using those zo1 zo2 zo3 zo4 ... zo10 variables.

Defining those variable is not problem using the eval command. My problem/difficulty is when I wish to use the content of those zo$k variable for other operations (such as a simple "echo" command; but it is in fact more complicated commands).
I need to call for the variable, but with no hard coding. I CANNOT use zo1 zo2... I need to use zo$k or equivalent.

My question is: how can I call for those variables based on the value of the subscript ($k) ?

I hope this is clearer.