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Bash Dictionary - Terrible Hack of the Day

So, I just had a reason to implement something like a dictionary in Bash.  Of course, I could try to determine if such a feature exists already (it does in Bash 4, alas the default on OS X seems to be 3.2), but why not just try to hack something together?

Here’s what I got initially:

value="$(eval echo '$OFFSETDICT'${keyToLookup})"
echo $value
>     21

So, that’s ridiculous.  Basically, the values are set in code with the dictionary name “OFFSETDICT”, and the key as whatever comes after the name {keyUno, keyTres, …}.  Then the value line builds a variable lookup and executes it.  That’s pretty lazy of me to write it like that, so here’s a function (a Bash function - so terrible).

function get {
echo $(eval echo "$CMD")

a=`get OFFSETDICT keyQuatro`
echo $a
>     21

Hrm, I wrote a getter, I should probably make a setter too.

function set {
eval "$CMD"

get OFFSETDICT keyCinco
set OFFSETDICT keyCinco "Sup my man?"
get OFFSETDICT keyCinco
>     Sup my man?

You can imagine what this does to the variable space.  But if you’re really worried about that, maybe don’t use Bash.

I really just needed to look up one value based on another value.  I guess an array would have worked, but that’s not much of a stupid hack.


finity - Dec 3, 2012

My use of eval here is truly the terrible part. If an untrusted user can supply any of the parameters that eval touches, that’s a very easy injection attack. I have no reason to run this code with any permissions other than the untrusted user’s, though, so this should be fine.