Ttyjfyk

I'm working through creating a Dockerfile that calls on a script named start.sh I want to take the environment variables that are passed from the user either by means of docker-compose.yml or docker run -e now what I've wanted to do is something where I have a list of these variables defined dynamically in an array.

## Environment Variables
## Missing Vars off the hop SLACK_HOOK_URL
CONFIG_SETTINGS=(
 AWS_ID
 AWS_SECRET
 BUCKET_REGION
 BUCKET_NAME
 DB_USER
 DB_PASSWORD
 DB_HOSTIP
 DB_PORT
 DB_NAME
)

I only have to unset a subset of the above variables defined in this array.

CONFIG_SECRETS=(
 AWS_ID
 AWS_ID_STR
 AWS_SECRET
 AWS_SECRET_STR
 BUCKET_NAME
 BUCKET_NAME_STR
 DB_USER
 DB_USER_STR
 DB_PASSWORD
 DB_PASSWORD_STR
 DB_HOSTIP
 DB_HOSTIP_STR
 DB_PORT
 DB_PORT_STR
 DB_NAME
 DB_NAME_STR
)

My problem is the following for loop.

## Sanitization section
for i in "$!CONFIG_SECRETS[@]"; do
 ## Nullify environment variables that contain secrets before launching.
 # echo $CONFIG_SECRETS[$i]
 eval $"$CONFIG_SECRETS[$i]"=$""
 unset $"$CONFIG_SECRETS[$i]"
 echo $$CONFIG_SECRETS[$i] is now to: $"$CONFIG_SECRETS[$i]"
done

For example, the below is a for loop I created to iterate through these variables and set them.

for i in "$!CONFIG_SETTINGS[@]"; do
 echo $CONFIG_SETTINGS[$i]"_KEY"
 ## Indirect references http://tldp.org/LDP/abs/html/ivr.html
 eval FROM_STRING=$"$CONFIG_SETTINGS[$i]_STR"
 eval VALUE_STRING=$$CONFIG_SETTINGS[$i]
 eval KEY_STRING=$"$CONFIG_SETTINGS[$i]_KEY"
 TO_STRING="$KEY_STRING$VALUE_STRING"
 sed -i '' "s/$FROM_STRING/$TO_STRING/g" ./config.tmpl
done

This modifies the following configuration file.

 "aws_id": "YOUR-AWS-ID",
 "aws_secret": "YOUR-AWS-SECRET",
 "bucket_region": "YOUR-BUCKET-REGION",
 "bucket_name": "YOUR-BUCKET-NAME",
 "db_conn": "USER:PASSWORD@tcp(localhost:3306)/DBNAME",
 "slack_hook_url": ""

The full context script minus things that are outside of the scope of this question.

#!/bin/bash

## Launch service will tell prism-bin what mode to run in.
LAUNCHMODE="$MODE:-$1"

## This variable will be what can override default launch args. I may modify this as I learn more about prism-bin
LAUNCHARGS="$CUSTOM_ARGS:-$2"

## This is setup this way to handle any situations that might arise from the
## config being JSON and bash not being any good at JSON.
# ## Strings to replace.
AWS_ID_STR="YOUR-AWS-ID"
AWS_SECRET_STR="YOUR-AWS-SECRET"
BUCKET_REGION_STR="YOUR-BUCKET-REGION"
BUCKET_NAME_STR="YOUR-BUCKET-NAME"
DB_USER_STR="USER"
DB_PASSWORD_STR="PASSWORD"
DB_HOSTIP_STR="localhost"
DB_PORT_STR="3306"
DB_NAME_STR="DBNAME"

# Environment Variables/Defaults
## Json sucks in BASH/Shell so you need to add trailing commas intermittently.
## Just pay attention to this. Also at some point I'll need to make a fringe
## case for handling key/values that aren't included in the default config.
AWS_ID="$AWS_ID:-potato"
AWS_SECRET="$AWS_SECRET:-potato"
BUCKET_REGION="$BUCKET_REGION:-potato"
BUCKET_NAME="$BUCKET_NAME:-potato"
DB_USER="$DB_USER:-potato"
DB_PASSWORD="$DB_PASSWORD:-potato"
DB_HOSTIP="$DB_HOSTIP:-potato"
DB_PORT="$DB_PORT:-potato"
DB_NAME="$DB_NAME:-potato"

## Environment Variables in Array
CONFIG_SETTINGS=(
 AWS_ID
 AWS_SECRET
 BUCKET_REGION
 BUCKET_NAME
 DB_USER
 DB_PASSWORD
 DB_HOSTIP
 DB_PORT
 DB_NAME
)
CONFIG_SECRETS=(
 AWS_ID
 AWS_ID_STR
 AWS_SECRET
 AWS_SECRET_STR
 BUCKET_NAME
 BUCKET_NAME_STR
 DB_USER
 DB_USER_STR
 DB_PASSWORD
 DB_PASSWORD_STR
 DB_HOSTIP
 DB_HOSTIP_STR
 DB_PORT
 DB_PORT_STR
 DB_NAME
 DB_NAME_STR
)

## Sanitization section
# Awaiting someone smarter than me to suggest a method for this.
# https://unix.stackexchange.com/questions/474097/i-want-to-unset-a-list-of-bash-variables-that-have-their-variable-strings-stored
for i in "$CONFIG_SECRETS[@]"; do
 unset $i
 eval echo $"$CONFIG_SECRETS[$i]"=$$CONFIG_SETTINGS[$i]
done

This should be a simple loop

#!/bin/bash

UNSET=(a b c)

a=10 b=20 c=30 d=40 e=50

echo Before a=$a b=$b c=$c d=$d e=$e

for i in $UNSET[@]
do
 unset $i
done

echo After a=$a b=$b c=$c d=$d e=$e

This results in

Before a=10 b=20 c=30 d=40 e=50
After a= b= c= d=40 e=50

You can dereference variables with !:

$ foo=bar
$ bar=1
$ echo $!foo
1

You can't use a variable inside an expansion like that though, so you will probably have to do something really ugly with eval.

I think you've worked yourself into a circle; simply loop over the array and unset the parameter referred to by the loop:

AWS_SECRET='secret_here'
echo Before:
declare -p AWS_SECRET
set|grep AWS_SECRET

for secret in "$CONFIG_SECRETS[@]"
do
 unset $secret
done

echo After:
declare -p AWS_SECRET
set|grep AWS_SECRET