Extended regex (grep -E) in Bash Scripting - Mini Project: Build & Apply

Filter Log Entries Using Extended Regex with grep -E

📖 Scenario: You have a system log file with various entries. You want to find all lines that mention either error or warning messages using a single command.

🎯 Goal: Build a bash script that uses grep -E with an extended regular expression to filter lines containing either error or warning from a log file.

📋 What You'll Learn

Create a variable logfile with the exact filename system.log

Create a variable pattern with the exact extended regex 'error|warning'

Use grep -E with $pattern and $logfile to filter matching lines

Print the filtered lines to the terminal

💡 Why This Matters

🌍 Real World

System administrators often need to scan log files for errors or warnings quickly. Using extended regex with grep helps filter relevant lines efficiently.

💼 Career

Knowing how to use grep with extended regex is a fundamental skill for troubleshooting and monitoring systems in IT and DevOps roles.

1

Create the log file variable

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

Bash Scripting

# Create a variable called logfile and set it to 'system.log'
# Your code here

Need a hint?

Use single quotes around the filename to assign it as a string.

2

Create the extended regex pattern variable

Create a variable called pattern and set it to the extended regex string 'error|warning'.

Bash Scripting

logfile='system.log'
# Create a variable called pattern and set it to 'error|warning'
# Your code here

Need a hint?

Use single quotes to keep the pipe character literal in the regex pattern.

3

Use grep -E with the pattern and logfile

Write a command using grep -E with the variables $pattern and $logfile to filter lines containing either 'error' or 'warning'.

Bash Scripting

logfile='system.log'
pattern='error|warning'
# Use grep -E with $pattern and $logfile to filter lines
# Your code here

Need a hint?

Use double quotes around variables to preserve their values in the command.

4

Print the filtered lines

Run the command to print the filtered lines containing 'error' or 'warning' from system.log.

Bash Scripting

logfile='system.log'
pattern='error|warning'
grep -E "$pattern" "$logfile"
# Print the filtered lines above

Need a hint?

Make sure your system.log file contains lines with 'error' and 'warning' to see output.