Problem with getting string value from array

_kostek_ · 10-29-2009, 05:17 AM

Hi All

I've got a problem...

a[0] = 22
echo $[a[0]]

echoes 22 - that works fine

a[0] = AB
echo $[a[0]]

echoes 0 - It doesn't work

a[0] = AB
echo ${a[0]}

echoes AB - that works fine as well

So my question is WHY "echo $[a[0]]" doesn't work properly with string and how I should declare
a[0] or do something else to make it work(maybe does it make difference running it in bash or ksh)??

It's necessary to make it work with $[a[0]] instead of ${a[0]}.

waiting for answers....

thanks

Hko · 10-29-2009, 06:05 AM

Quote:

Originally Posted by _kostek_

It's necessary to make it work with $[a[0]] instead of ${a[0]}.

No. Not possible in bash.
The way to dereference an array member in bash is ${a[0]}.

_kostek_ · 10-29-2009, 06:49 AM

Quote:

Originally Posted by Hko

No. Not possible in bash.
The way to dereference an array member in bash is ${a[0]}.

OK maybe I describe why is $[a[0]] so important

I put my scripts in some environment(I dont have permissions to change variable values in this environment). There is requirement in documentation regarding scripts to use $[a[0]] to make them flexible(administrator changes variable values and run the scripts).
When I use $[a[0]] in my script and run it under environment IT WORKS!!!
SO HOW IT IS DONE ??

In order to test my scripts I just want to simulate the environment, set the variables as I want avoiding changing scripts($[a[0]] to ${a[0]})

I hope it's clear :-)

catkin · 10-29-2009, 01:05 PM

Quote:

Originally Posted by _kostek_

I put my scripts in some environment

This is very puzzling; I don't understand why bash is doing what you reported. I can reproduce what you reported and found it is doing some sort of arithmetic

Code:

c:~$ a[0]=22
c:~$ echo $[a[0]]
22
c:~$ a[0]=AB
c:~$ echo $[a[0]]
0
c:~$ a[0]=22A
c:~$ echo $[a[0]]
bash: 22A: value too great for base (error token is "22A")

I have not found anything illuminating in the GNU Bash Reference Manual, the POSIX Shell Command Language Specifications and the Korn Shell man page. To make matters worse, Google and heapr cannot search for "$["

What is the environment that you put your scripts in?

bgeddy · 10-29-2009, 02:08 PM

The interpretation of the "$[]" is called Bash arithmetic expansion. The use of "[]" is apparently now deprecated and left at only "(())" . Here's a reference to it. You can try substituting the recommended "(())" for the "[]" and see that you get the same results.

catkin · 10-31-2009, 11:11 AM

Quote:

Originally Posted by bgeddy

The interpretation of the "$[]" is called Bash arithmetic expansion. The use of "[]" is apparently now deprecated and left at only "(())" . Here's a reference to it. You can try substituting the recommended "(())" for the "[]" and see that you get the same results.

Thanks bgeddy

I wonder how old it is that it's not in the primary bash references but is on linux.about.com