System logs (/var/log) in Linux CLI - Mini Project: Build & Apply

System Logs Analysis with Linux CLI

📖 Scenario: You are a system administrator who needs to check system logs stored in the /var/log directory. These logs help you understand what is happening on your Linux system.One common task is to find error messages in the system log file /var/log/syslog.

🎯 Goal: Build a simple script that reads the /var/log/syslog file, filters out lines containing the word error (case insensitive), and counts how many error lines are found.

📋 What You'll Learn

Create a variable holding the path to /var/log/syslog

Create a variable holding the keyword error

Use grep with the keyword variable to filter lines from the log file

Count the number of matching lines

Print the count with a clear message

💡 Why This Matters

🌍 Real World

System administrators often need to check logs to find errors or warnings quickly. This script helps automate that task.

💼 Career

Knowing how to use Linux command line tools like grep and wc is essential for troubleshooting and monitoring servers.

1

Set the log file path

Create a variable called logfile and set it to the string /var/log/syslog.

Linux CLI

logfile="/var/log/syslog"
# Your code here

Need a hint?

Use logfile="/var/log/syslog" to store the log file path.

2

Set the keyword to search

Create a variable called keyword and set it to the string error.

Linux CLI

logfile="/var/log/syslog"
keyword="error"
# Your code here

Need a hint?

Use keyword="error" to store the search word.

3

Filter and count error lines

Use grep with the -i option and the variable keyword to filter lines from the file stored in logfile. Then use wc -l to count the matching lines. Store the count in a variable called error_count.

Linux CLI

logfile="/var/log/syslog"
keyword="error"
error_count=$(grep -i "$keyword" "$logfile" | wc -l)
# Your code here

Need a hint?

Use error_count=$(grep -i "$keyword" "$logfile" | wc -l) to count error lines.

4

Print the error count

Print the message "Number of error lines: " followed by the value of error_count using echo.

Linux CLI

logfile="/var/log/syslog"
keyword="error"
error_count=$(grep -i "$keyword" "$logfile" | wc -l)
echo "Number of error lines: $error_count"
# Your code here

Need a hint?

Use echo "Number of error lines: $error_count" to display the result.