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?

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."