Kubernetes POD Command and argument - kubernetes

Question

I am learning kubernetes and have the following question related to command and argument syntax for POD.
Are there any specific syntax that we need to follow to write a shell script kind of code in the arguments of a POD? For example
In the following code, how will I know that the while true need to end with a semicolon ; why there is no semi colon after do but after If etc
while true;
do
echo $i;
if [ $i -eq 5 ];
then
echo "Exiting out";
break;
fi;
i=$((i+1));
sleep "1";
done
We don't write shell script in the similar way from semicolon prespective so why do we have to do this in POD.
I tried the command in /bin/bash format as well
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: null
labels:
run: bash
name: bash
spec:
containers:
- image: nginx
name: nginx
args:
- /bin/bash
- -c
- >
for i in 1 2 3 4 5
do
echo "Welcome $i times"
done
resources: {}
dnsPolicy: ClusterFirst
restartPolicy: Always
status: {}
Error with new code
/bin/bash: -c: line 2: syntax error near unexpected token `echo'
/bin/bash: -c: line 2: ` echo "Welcome $i times"'

Answer 1

Are there any specific syntax that we need to follow to write a shell script kind of code in the arguments of a POD?
No, shell syntax is the same across.
...how will I know that the while true need to end with a semicolon
Used | for your text block to be treated like an ordinary shell script:
...
args:
- /bin/bash
- -c
- |
for i in 1 2 3 4 5
do
echo "Welcome $i times"
done
When you use > your text block is merge into a single line where newline is replaced with white space. Your command become invalid in such case. If you want your command to be a single line, then write them with ; like you would in ordinary terminal. This is shell scripting standard and is not K8s specific.
If you must use >, you need to either add empty line or indented the next line correctly:
apiVersion: v1
kind: Pod
metadata:
labels:
run: bash
name: bash
spec:
containers:
- image: nginx
name: nginx
args:
- /bin/bash
- -c
- >
for i in 1 2 3 4 5
do
echo "Welcome $i times"
done
restartPolicy: Never
kubectl logs bash to see the 5 echos and kubectl delete pod bash to clean-up.