Split string and extract variables with shell script - shell

Question

Question
Given this single-line string:
PG_USER=postgres PG_PORT=1234 PG_PASS=icontain=and*symbols
What would be the right way to assign each value to its designated variable so that I can use it afterward?
Context
I'm parsing the context of a k8s secret within a CronJob so that I can periodically call a Stored Procedure in our Postgres database.
To do so, I plan on using:
PG_OUTPUT_VALUE=$(PGPASSWORD=$PG_PASSWD psql -qtAX -h $PG_HOST -p $PG_PORT -U $PG_USER -d $PG_DATABASE -c $PG_TR_CLEANUP_QUERY)
echo $PG_OUTPUT_VALUE
The actual entire helm chart I'm currently trying to fix looks like this:
apiVersion: batch/v1beta1
kind: CronJob
metadata:
name: {{ template "fullname" $ }}-tr-cleanup-cronjob
spec:
concurrencyPolicy: Forbid
schedule: "* * * * *"
jobTemplate:
spec:
template:
spec:
restartPolicy: OnFailure
volumes:
- name: postgres
secret:
secretName: {{ template "fullname" $ }}-postgres
containers:
- name: {{ template "fullname" $ }}-tr-cleanup-pod
image: postgres:12-alpine
imagePullPolicy: Always
env:
- name: PG_PROPS
valueFrom:
secretKeyRef:
name: {{ template "fullname" $ }}-postgres
key: postgres.properties
command:
- /bin/sh
- -c
- echo "props:" && echo $PG_PROPS && PG_USER=$(grep "^PG_USER=" | cut -d"=" -f2-) && echo $PG_USER && PG_TR_CLEANUP_QUERY="SELECT something FROM public.somewhere;" && echo $PG_TR_CLEANUP_QUERY && PG_OUTPUT_VALUE=$(PGPASSWORD=$PG_PASSWD psql -qtAX -h $PG_HOST -p $PG_PORT -U $PG_USER -d $PG_DATABASE -c $PG_TR_CLEANUP_QUERY) && echo PG_OUTPUT_VALUE
volumeMounts:
- name: postgres
mountPath: /etc/secrets/postgres
Current approach
As you can see, I'm currently using:
PG_USER=$(grep "^PG_USER=" | cut -d"=" -f2-)
That is because I initially thought the secret would be output on multiple lines, but it turns out that I was wrong. The echo $PG_USER displays an empty string.

Answer 1

The bash declare command is appropriate here, and is safer than eval.
Suppose the input contains something potentially malicious
line='PG_USER=postgres PG_PORT=1234 PG_PASS=icontain=and*symbols`ls`'
I'm assuming none of the values contain whitespace. Let's split that string
read -ra assignments <<< "$line"
Now, declare each one
for assignment in "${assignments[#]}"; do declare "$assignment"; done
Everywhere we examine the input, we maintain double quotes.
Let's see what we ended up with:
$ declare -p PG_USER PG_PORT PG_PASS
declare -- PG_USER="postgres"
declare -- PG_PORT="1234"
declare -- PG_PASS="icontain=and*symbols\`ls\`"

Answer 2

Option 1
This function can be reused to assign each variable individually:
extract() {
echo "$INPUT" | grep -o "$1=.*" | cut -d" " -f1 | cut -d"=" -f2- ;
}
And to use it:
PG_USER=$(extract PG_USER)
PG_PORT=$(extract PG_PORT)
PG_PASS=$(extract PG_PASS)
Option 2
Another potential solution, with a security concern, is to simply use:
eval "$INPUT"
It should only be used if you have validated the input.
Contextual complete answer
And because I've presented the k8s context in the question, here is the answer as plugged into that solution.
apiVersion: batch/v1beta1
kind: CronJob
metadata:
name: {{ template "fullname" $ }}-cronjob
spec:
concurrencyPolicy: Forbid
schedule: "* * * * *"
jobTemplate:
spec:
template:
spec:
restartPolicy: OnFailure
volumes:
- name: postgres
secret:
secretName: {{ template "fullname" $ }}-postgres
containers:
- name: {{ template "fullname" $ }}-cronjob-pod
image: postgres:12-alpine
imagePullPolicy: Always
env:
- name: PG_PROPS
valueFrom:
secretKeyRef:
name: {{ template "fullname" $ }}-postgres
key: postgres.properties
command:
- /bin/sh
- -c
- >-
extract() { echo "$PG_PROPS" | grep -o "$1=.*" | cut -d" " -f1 | cut -d"=" -f2- ; } &&
export PGHOST=$(extract PG_HOST) &&
export PGPORT=$(extract PG_PORT) &&
export PGDATABASE=$(extract PG_DATABASE) &&
export PGUSER=$(extract PG_USER) &&
PG_SCHEMA=$(extract PG_SCHEMA) &&
PG_QUERY="SELECT tenant_schema FROM $PG_SCHEMA.tenant_schema_mappings;" &&
PGPASSWORD=$(extract PG_PASSWD) psql --echo-all -c "$PG_QUERY"
volumeMounts:
- name: postgres
mountPath: /etc/secrets/postgres