Iterating an ordered path variable in a for loop - bash

Question

I have the following txt document:
deviceIDs.txt
UDID0=LGH811dec0bfd6
UDID1=41006289e4b2a179
UDID2=d9a7aa45
PORT0=4567
PORT1=4568
PORT2=4569
BOOTPORT0=5556
BOOTPORT1=5557
BOOTPORT2=5558
I want to be able to write the following bash script:
#!/bin/bash
source /path/deviceIDs.txt
for ((i=0;i<=2;i++))
do
echo $UDID$i
echo $PORT$i
echo $BOOTPORT$i
done
however this doesn't work. Presumable because the dollar sign is being used twice in one expression. I've tried formatting the variables using {} too but still no success.

Answer 1

You can use bash's form of indirection:
#!/bin/bash
source deviceIDs.txt
for ((i=0;i<=2;i++))
do
for x in UDID PORT BOOTPORT
do
y=$x$i
echo ${!y}
done
done
The key here is that ${!y} returns the value of the variable that is named by y.
This produces the output:
LGH811dec0bfd6
4567
5556
41006289e4b2a179
4568
5557
d9a7aa45
4569
5558
Alternative
If we are allowed to change the data file format, consider defining your variables as arrays this way:
$ cat IDarrays.txt
UDID=(LGH811dec0bfd6 41006289e4b2a179 d9a7aa45)
PORT=(4567 4568 4569)
BOOTPORT=(5556 5557 5558)
With that, the script can be written:
#!/bin/bash
source IDarrays.txt
for ((i=0;i<=2;i++))
do
echo ${UDID[$i]}
echo ${PORT[$i]}
echo ${BOOTPORT[$i]}
done

Answer 2

I didn't knew John1024's solution with !y.
If you can't modify deviceIDs.txt because it is generated by someone out of your control, you could use arrays like this too:
#!/bin/bash
source /path/deviceIDs.txt
u=($UDID{0..2});p=($PORT{0..2});b=($BOOTPORT{0..2})
for i in {0..2}; do echo -e ${u[i]}"\n"${p[i]}"\n"${b[i]}"\n"; done
LGH811dec0bfd6
4567
5556
41006289e4b2a179
4568
5557
d9a7aa45
4569
5558