eval, array, number of elements - couldn't get it

alex_5161 · #1 (**permalink**) 07-01-2008

I try to get a number of elements in an array, using dynamic array name.
I need the array name to be dynamic.

The array name is constructed as 'inf_ln_$nmb', where $nmb is a file line number
So, say I have the arr 'inf_ln_4':

Code:

> for (( el=0; el<${#inf_ln_4[*]}; el++ )); do 
>    echo "$el: >"${inf_ln_4[$el]}"<"; 
> done
0: >Address 2<
1: >Memphis, TN 38134<
2: ><
3: >31<
4: >11/1/2003<
5: >6/30/2004<
6: >00018906465 MAC 01<
7: >TRUE<
8: ><
9: ><
> # or :
>  echo ${inf_ln_4[@]}
Address 2 Memphis, TN 38134 31 11/1/2003 6/30/2004 00018906465 MAC 01 TRUE

I do next:

Code:

>
>a=4;  # this is to be used for dynamic array's name 
> eval echo ${inf_ln_$a[@]}     # expect 'eval' will replace $a for  4
bash: ${inf_ln_$a[@]}: bad substitution
>
> # the same I have by trying to access an array element:
> eval ec ${inf_ln_$a[0]}
bash: ${inf_ln_$a[0]}: bad substitution

Is there a way to prevent the bash-shell from treat the '$a[0]' as a substitution?

My main attempt is to copy the current dynamicaly numbered array to some staticly-named array to comfortably work with it's element

Appreciate your advise or help!
Alex

alex_5161 · #2 (**permalink**) 07-01-2008

I have found it by myself:

Code:

 eval echo $\{#inf_ln_$a[@]\}
> 10

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