Five Powerful Uses of the grep Command in Linux

Master the art of searching with grep on the command line

Introduction

The grep command is one of the most frequently used tools in Unix/Linux environments. Whether you are a system administrator, developer, or a curious power user, learning how to use grep can drastically improve your productivity. In this post, we’ll explore five practical and powerful uses of the grep command.

1. Search for a Word in a File

One of the most basic uses of grep is to search for a specific word in a file.

grep "error" logfile.txt

This command searches for the word “error” in logfile.txt and prints all matching lines. It’s perfect for troubleshooting log files.

2. Recursive Search in Directories

Use -r or --recursive to search within all files in a directory and its subdirectories.

grep -r "TODO" ./project-folder

This is useful for developers who want to locate all TODO comments in a codebase.

3. Ignore Case While Searching

The -i option allows you to perform a case-insensitive search.

grep -i "warning" system.log

This will match “Warning”, “WARNING”, “warning”, and so on.

4. Count Occurrences

The -c flag counts the number of lines that match the pattern.

grep -c "failed" auth.log

Use this to quickly get the number of failed login attempts, for example.

5. Display Only Matching Text

If you only want to display the matching portion of the line, use the -o option.

grep -o "[0-9]\{3\}-[0-9]\{3\}-[0-9]\{4\}" contacts.txt

This will extract phone numbers from the file using a regular expression pattern.

Conclusion

These five examples just scratch the surface of what grep can do. Whether you're analyzing logs, scanning code, or debugging output, mastering grep is essential for efficient command-line usage.