Service health check script in Bash Scripting - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this service health check snippet?

Consider this bash script snippet that checks if the nginx service is active and prints a message accordingly. What will it output if nginx is running?

Bash Scripting

if systemctl is-active --quiet nginx; then
  echo "nginx is running"
else
  echo "nginx is not running"
fi

A nginx is running

B syntax error

C command not found error

D nginx is not running

💡 Hint

The command 'systemctl is-active --quiet' returns success if the service is active.

The script uses 'systemctl is-active --quiet nginx' which returns exit code 0 if nginx is running, so the if condition is true and prints 'nginx is running'.

📝 Syntax

intermediate

Identify the syntax error in this health check script

This script aims to check if the apache2 service is running and print a message. Which option correctly identifies the syntax error?

Bash Scripting

if systemctl is-active apache2; then
  echo "apache2 is running"
else
  echo "apache2 is not running"
fi

A Missing '--quiet' option causes output to appear but no syntax error

B Missing semicolon after 'then' causes syntax error

C Incorrect use of brackets causes syntax error

D Missing 'then' keyword causes syntax error

💡 Hint

Check if the script syntax is valid but consider the command behavior.

The script is syntactically correct. The only issue is that 'systemctl is-active apache2' without '--quiet' outputs the status text, but this does not cause a syntax error.

🔧 Debug

advanced

Why does this health check script always print 'Service is not running'?

This script checks if the mysql service is running but always prints 'Service is not running' even when mysql is active. What is the cause?

Bash Scripting

if systemctl is-active mysql; then
  echo "Service is running"
else
  echo "Service is not running"
fi

A The command 'systemctl is-active mysql' returns output but exit code is non-zero, causing else branch

B The script lacks '--quiet' so output interferes with condition evaluation

C The 'if' condition checks output string instead of exit code, causing wrong branch

D The script uses wrong service name causing failure

💡 Hint

Check how bash evaluates the 'if' condition with commands that output text.

In bash, 'if' checks the exit status of the command, not its output. 'systemctl is-active mysql' outputs text but returns 0 if active. If the script captures output incorrectly, it may cause wrong evaluation.

🚀 Application

advanced

Which script correctly checks multiple services and reports their status?

You want a bash script to check if 'nginx' and 'redis' services are running and print their status lines. Which script does this correctly?

A

for svc in nginx redis
  if systemctl is-active --quiet $svc; then
    echo "$svc is running"
  else
    echo "$svc is not running"
  fi
done

B

for svc in nginx redis; do
  if systemctl status $svc; then
    echo "$svc is running"
  else
    echo "$svc is not running"
  fi
done

C

for svc in nginx redis; do
  if systemctl is-active $svc; then
    echo "$svc is running"
  else
    echo "$svc is not running"
  fi
done

D

for svc in nginx redis; do
  if systemctl is-active --quiet $svc; then
    echo "$svc is running"
  else
    echo "$svc is not running"
  fi
done

💡 Hint

Check for correct loop syntax and quiet status check.

Option D uses correct for-loop syntax with semicolon and 'systemctl is-active --quiet' to check service status silently. Option D misses semicolon after 'redis'. Option D lacks '--quiet' so output may interfere. Option D uses 'systemctl status' which outputs text and always returns 0, causing wrong results.

🧠 Conceptual

expert

What is the best way to handle transient service states in a health check script?

When a service may be restarting or temporarily inactive, how should a bash health check script handle this to avoid false 'not running' reports?

A Use 'systemctl status' once and parse output for 'running' keyword

B Run 'systemctl is-active --quiet' multiple times with delays and confirm consistent inactive status before reporting

C Check service logs instead of status commands for more accurate state

D Assume service is running if last check was successful, ignore current status

💡 Hint

Transient states can cause momentary false negatives; repeated checks help confirm.

Transient states like restarting can cause a single check to report inactive. Repeating checks with short delays reduces false alarms. Parsing logs or assuming previous state is unreliable.