Bash Scripting in Linux Variable/Array Assignment

Question

I'm trying to make my shell script similar to ordering at a fast food restaurant. However, I'm confused as to how to set arrays to determine the size of the drink the customer wishes to order. My sizes are as follows:

small=12oz
medium=16oz
large=20oz
xlarge =24oz

I have my shell script programmed to read the customers input for $size but I don't know how to translate the word "small" into an oz amount when customer declares their size. I as going to use the eval“$size="` option but what do I put so that it can vary? Will x be sufficient?

Thanks!

You could use variable indirection (retrieve the value of the variable whose name is specified as the value of $size), but a better practice would be to use associative arrays, which you will find explained here — Aaron
– Aaron, Commented Oct 29, 2018 at 16:51

Paul Hodges · Accepted Answer · 2018-10-29 17:02:37Z

4

Try an associative lookup.

$: declare -A drink=(
    [small]=12oz
    [medium]=16oz
    [large]=20oz
   )
$: choice=medium
$: echo "${drink[$choice]}"
16oz
$: drink[xlg]=32oz
$: choice=xlg
$: echo "${drink[$choice]}"
32oz

Watch the syntax, though, it's kind of a pain.

edited Oct 29, 2018 at 17:02

answered Oct 29, 2018 at 16:56

Paul Hodges

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2 Comments

chepner Over a year ago

You need to declare size as an associative array first, or it defaults to being an indexed array. Notice in your example that ${size[$choice]} outputs 20oz, not 16oz as would be expected, because each of your assignments sets (and resets) size[0] as the strings are evaluated as variable names in the arithmetic contexts.

Linda N Over a year ago

Thank you so much! I was having difficulty understanding the concepts of arrays. I understand how to set but I was confused on how to get it called back into my program. I'm just learning how to script and there's a lot of ways to get the job done!

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