How to use array values as substitutes for names of other arrays

Question

I am still new to Bash and can only use Bash 3 at work. I'm trying to build a process that will allow me to connect to all of our databases (DEV/TEST/PROD).

I have a file named environments.sh

#!/bin/bash
## 0 = Password, 1 = HOST, 2 = SERVICENAME

## List of all Environments
ENV[0]=DEV
ENV[1]=TEST
ENV[2]=PROD

## Dev Env Details
DEV[0]=SU_DBA_201503
DEV[1]=xxxxxx-Dev-xx.xxx.xxx.xxx  #<-- I edited this for security purposes
DEV[2]=dev.xxx.xxx 

## Test Env Details
TEST[0]=DBA_PN_0002
TEST[1]=xxxxxx-Test-xx.xxx.xxx.xxx
TEST[2]=test.xxx.xxx

## Prod Env Details
PROD[0]=TM_DB_US7a6a
PROD[1]=xxxxxx-Prod-xx.xxx.xxx.xxx
PROD[2]=prod.xxx.xxx

So essentially, my goal is to loop through all environments (DEV, TEST, PROD) and access each array's attributes to build a connection string.

At this point I have a new file (for testing purposes, I've callit it looper.csh:

#!/bin/bash

#Get environments
source ./environments.sh

for env in ${ENV[@]}
do
    echo Current Env $env
    cur_env=$env
    for attr in ${cur_env[@]}
    do
    # Will eventually build connection string but for now, just want to echo
        echo $attr
    done
done

But when I run this, it gives me an error on the line:

for attr in ${cur_env[@]}

I've tried a few different ways to substitute this correctly, but I'm not sure what I'm doing wrong.

Any and all guidance would be greatly appreciated.

.csh with a #!/bin/bash hashbang? You may want to check that naming. — ilkkachu, Feb 07 '18 at 18:15

score 2 · Accepted Answer · edited Feb 07 '18 at 18:07

2

I'd suggest indirect variable references:

source ./environments.sh

for env in "${ENV[@]}"
do
    cur_env="${env}[@]"
    for attr in "${!cur_env}"
    do
        # whatever
    done
done

Note the ! before the cur_env in the for attr, it means use the value of the variable named in this var which on the first round will be DEV[@]

edited Feb 07 '18 at 18:07

ilkkachu

138,973

answered Feb 06 '18 at 23:25

XrXca

119

I added quotes around the ${!cur_env}, so values can have spaces if desired etc. – XrXca Feb 06 '18 at 23:37
This works perfectly! Thank you very much for you help. I'm not familiar with indirect variables so I will look these up. Thanks again! – need_java Feb 06 '18 at 23:41
@XrXca: You shouldn't only quote variables "so values can have spaces". You should always quote variables. Security implications of forgetting to quote a variable in bash/POSIX shells – jesse_b Feb 06 '18 at 23:45
Note that associative array keys aren't stored in the order you declare them, so the for loop isn't guaranteed to go in dev->test->prod order. Not sure if this is an issue in this case, just pointing this out. – m0dular Feb 07 '18 at 17:33
1

@m0dular, there's no associative arrays here, just regular integer-indexed ones. Bash 3 doesn't even support them, and that's what the OP said they're stuck with. – ilkkachu Feb 07 '18 at 18:08
@ilkkachu Whoops! I'm so used to array+=() syntax I totally missed that. Thanks for pointing this out. – m0dular Feb 07 '18 at 18:11

How to use array values as substitutes for names of other arrays

1 Answers1