tail -f for live log monitoring in Linux CLI - Mini Project: Build & Apply

Using tail -f for Live Log Monitoring

📖 Scenario: You are a system administrator who needs to watch the latest entries of a server log file as they happen. This helps you quickly spot errors or important events without opening the file repeatedly.

🎯 Goal: Learn how to use the tail -f command to monitor a log file live in the terminal.

📋 What You'll Learn

Create a sample log file with specific lines

Add a helper variable for the log file name

Use tail -f command to follow the log file

Display the live output of the log file

💡 Why This Matters

🌍 Real World

System administrators and developers often need to watch log files live to quickly detect errors or important events as they happen.

💼 Career

Knowing how to use <code>tail -f</code> is a basic but essential skill for monitoring servers, debugging applications, and maintaining system health.

1

Create a sample log file

Create a file called app.log with these exact three lines:
INFO: Application started
WARNING: Low disk space
ERROR: Failed to connect to database

Linux CLI

# Create the file app.log with the specified lines
# Your code here

Need a hint?

Use echo -e with newline characters \n and redirect output to app.log.

2

Set a variable for the log file name

Create a variable called logfile and set it to the string app.log.

Linux CLI

echo -e "INFO: Application started\nWARNING: Low disk space\nERROR: Failed to connect to database" > app.log
# Create variable logfile with value 'app.log'
# Your code here

Need a hint?

Use logfile="app.log" to assign the filename to a variable.

3

Use tail -f to follow the log file

Use the command tail -f $logfile to follow the log file live.

Linux CLI

echo -e "INFO: Application started\nWARNING: Low disk space\nERROR: Failed to connect to database" > app.log
logfile="app.log"
# Use tail -f to follow the logfile
# Your code here

Need a hint?

Use tail -f "$logfile" to watch the file as it updates.

4

Display the live output

Run the script and observe the output showing the three log lines live.

Linux CLI

echo -e "INFO: Application started\nWARNING: Low disk space\nERROR: Failed to connect to database" > app.log
logfile="app.log"
tail -f "$logfile"
# Run the command and observe output
# Your code here

Need a hint?

Run the script in a terminal. You should see the three log lines displayed and the command will keep running to show new lines if added.