exit-code-conditional

Check Command Result

We can check for the exit code of the last executed shell command by examining the $? variable.

kubectl get pods | grep auth-server
echo $?  # Prints 0 if auth-server is found in the output of kubectl, prints 1 otherwise.

Conditional

We can integrate running a command and use an if-then-fi statement block to check on the command's exit code. We can do this.

kubectl get pods | grep auth-server
if [ $? -eq 0 ]; then
  echo 'found'
else
  echo 'not found'
fi

We can also do this...

kubectl get pods | grep auth-server && echo 'found' || echo 'not found'

While the above examples are legit and works, they are in general not a good practice. Read here and here for why && || and command if [ $? -eq 0 ]; then... are bad respectively.

The preferred way is:

if kubectl get pods | grep auth-server; then
  echo 'found'
else
  echo 'not found'
fi

Alternatively...

if ! kubectl get pods | grep auth-server; then
  echo 'not found'
else
  echo 'found'
fi