When you work with Linux, you often need to find a specific line inside a file without opening it or scrolling through pages of text. This is exactly what the grep command is designed to do.

In this guide, you’ll learn how to use grep step by step in the terminal. We’ll start with the simplest working version and build confidence gradually. No shortcuts, no assumptions, and no unnecessary details.

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What grep Does

The grep command searches for text inside files.

You give it:

• A word or phrase to look for

• A file to search

It then shows only the lines that match. That’s all you need to know to get started.

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Creating a Simple File to Search

Before using grep, it helps to have a small file to work with so the behavior is easy to see.

Run this command:

printf "web01 running\nweb02 stopped\ndb01 running\nbackup01 running\n" > servers.txt

This creates a file called servers.txt and fills it with sample data.

You won’t see any output. In Linux, many commands stay silent when they succeed.

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The Simplest grep Command

The basic structure of grep looks like this:

grep "word" filename

Now try it for real:

grep "running" servers.txt

Output:

web01 running 
db01 running 
backup01 running

grep scanned the file line by line and printed only the lines that contain the word running. Everything else was ignored.

This is useful when checking server lists or status files without opening them.

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When No Matches Are Found

If grep doesn’t find a match, it stays quiet.

grep "offline" servers.txt

There is no output. This is expected behavior, not an error. Many scripts rely on this silence to confirm that something is missing.

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Case Sensitivity in Linux

By default, grep is case sensitive. On Linux, uppercase and lowercase letters are treated as different characters.

grep "Running" servers.txt

This produces no output because the file contains lowercase running.

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Ignoring Case Safely

To ignore case differences, add the -i option:

grep -i "Running" servers.txt

Output:

web01 running 
db01 running 
backup01 running

This makes searching safer when you’re unsure how text is formatted, especially in log files.

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Showing Line Numbers

Sometimes you want to know where a match appears in a file. The -n option adds line numbers.

grep -n "running" servers.txt

Output:

1:web01 running 
3:db01 running 
4:backup01 running

The number before the colon shows the line number, which is helpful when opening the file in an editor.

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Common Beginner Mistakes

Forgetting the filename

grep "running"

When starting out, grep always needs a filename.

Confusion about quotes

Quotes are the safest option, especially when searching for words with spaces or special characters:

grep "running" servers.txt

Thinking silence means failure

In Linux, no output often means success. It simply means nothing matched.

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A Practical Real-World Example

A common use of grep is checking log files for specific messages. On many systems, logs live in the /var/log directory.

grep -i "started" /var/log/syslog

This quickly confirms whether a service reported that it started. If the file doesn’t exist or requires extra permissions, that can be handled later.

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A Small Next Step

Once the basics feel comfortable, you can search multiple files at once:

grep "running" *.txt

*.txt means all files ending in .txt in the current directory. This is handled by the shell, not by grep itself. Don’t move past this until the core command feels natural.

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Conclusion

grep is one of the most useful tools in Linux, and you don’t need to master everything at once. Start with simple searches, pay attention to the output, and practice a few times.

With repetition, this command will quickly feel natural and reliable.