linux - How can I generate new variable names on the fly in a shell script?

Question

I'm trying to generate dynamic var names in a shell script to process a set of files with distinct names in a loop as follows:

#!/bin/bash

SAMPLE1='1-first.with.custom.name'
SAMPLE2='2-second.with.custom.name'

for (( i = 1; i <= 2; i++ ))
do
  echo SAMPLE{$i}
done

I would expect the output:

1-first.with.custom.name
2-second.with.custom.name

but i got:

SAMPLE{1}
SAMPLE{2}

Is it possible generate var names in the fly?

question from:https://stackoverflow.com/questions/10820343/how-can-i-generate-new-variable-names-on-the-fly-in-a-shell-script

Answer 1

You need to utilize Variable Indirection:

SAMPLE1='1-first.with.custom.name'
SAMPLE2='2-second.with.custom.name'

for (( i = 1; i <= 2; i++ ))
do
   var="SAMPLE$i"
   echo ${!var}
done

From the Bash man page, under 'Parameter Expansion':

"If the first character of parameter is an exclamation point (!), a level of variable indirection is introduced. Bash uses the value of the variable formed from the rest of parameter as the name of the variable; this variable is then expanded and that value is used in the rest of the substitution, rather than the value of parameter itself. This is known as indirect expansion."