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Linux Command Line Mastery · Lesson

Advanced `grep` and `find` Patterns

Utilize complex regex with `grep` and advanced criteria with `find` for precise searches.

Advanced `grep` and `find` Patterns is a free Linux Command Line Mastery lesson on CoddyKit — lesson 2 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Linux Command Line Mastery learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

Beyond Basic Searches

Welcome back! In previous lessons, you've learned the basics of grep for filtering text and find for locating files.

Today, we'll dive into advanced patterns. This means using more powerful regular expressions with grep and sophisticated criteria with find to achieve highly precise searches.

Enhanced `grep` with ERE

The standard grep command uses Basic Regular Expressions (BRE). For more power, we often switch to Extended Regular Expressions (ERE).

  • Use the -E option (or egrep) to enable ERE.
  • ERE allows features like + (one or more), ? (zero or one), | (OR), and () for grouping without needing to escape them.

ERE Example: One or More (`+`)

The + metacharacter matches one or more occurrences of the preceding character or group. For example, colou+r would match "colour" and "colouur" but not "color".

Try running this example:

#!/bin/bash
# Create a test file
echo "color" > my_text.txt
echo "colour" >> my_text.txt
echo "colouur" >> my_text.txt

echo "Searching for 'colou+r':"
grep -E "colou+r" my_text.txt

# Clean up
rm my_text.txt

ERE Example: Zero or One (`?`)

The ? metacharacter matches zero or one occurrence of the preceding character or group. It's useful for optional characters.

For instance, colou?r would match "color" (zero 'u') and "colour" (one 'u').

Run this to see it in action:

#!/bin/bash
# Create a test file
echo "color" > my_text.txt
echo "colour" >> my_text.txt
echo "colouur" >> my_text.txt

echo "Searching for 'colou?r':"
grep -E "colou?r" my_text.txt

# Clean up
rm my_text.txt

ERE Example: OR Logic (`|`)

The | metacharacter acts as an OR operator, allowing you to match one pattern or another. Parentheses () are used for grouping patterns.

For example, (cat|dog)s matches "cats" or "dogs".

Here's a quick demo:

#!/bin/bash
# Create a test file
echo "apple" > fruits.txt
echo "banana" >> fruits.txt
echo "orange" >> fruits.txt
echo "grape" >> fruits.txt

echo "Searching for 'apple' OR 'orange':"
grep -E "apple|orange" fruits.txt

# Clean up
rm fruits.txt

Advanced `find`: Modification Time (`-mtime`)

Beyond just names, find can locate files based on when they were last modified. The -mtime option is key here.

  • -mtime N: Files modified exactly N*24 hours ago.
  • -mtime +N: Files modified more than N*24 hours ago.
  • -mtime -N: Files modified less than N*24 hours ago.

For example, find . -mtime -7 finds files modified in the last 7 days.

Advanced `find`: Access Time & Size

You can also search by access time (when a file was last read) and file size:

  • -atime N: Files last accessed N*24 hours ago.
  • -size N[cwbkMG]: Files of a specific size.

Size units: c (bytes), w (two-byte words), b (512-byte blocks, default), k (KB), M (MB), G (GB).

Example: find . -size +1M finds files larger than 1MB.

#!/bin/bash
# Create a test file (1.5MB approx)
head -c 1500K /dev/urandom > large_file.bin
touch -a large_file.bin # Access now for -atime

echo "Finding files larger than 1MB:"
find . -size +1M -name "large_file.bin"

# Clean up
rm large_file.bin

Combining `find` Criteria

find commands are powerful because you can combine multiple criteria. By default, criteria are combined with an implicit AND.

You can also use:

  • -a: Explicit AND (often omitted).
  • -o: OR operator.
  • ( ): Parentheses for grouping (must be escaped or quoted in shell).

Example: find . -type f -name "*.txt" -o -name "*.log" finds all .txt OR .log files.

#!/bin/bash
# Create test files
touch file1.txt
touch file2.log
touch file3.md

echo "Finding .txt OR .log files:"
find . \( -name "*.txt" -o -name "*.log" \)

# Clean up
rm file1.txt file2.log file3.md

`find` and `-exec` for Actions

One of find's most powerful features is -exec, which allows you to run a command on each file or directory found.

  • -exec COMMAND {} \;: Runs COMMAND for each found item, replacing {} with the item's path. The \; marks the end of the command.
  • -exec COMMAND {} +: Runs COMMAND once with all found items as arguments. More efficient for many files.
#!/bin/bash
# Create some empty files
touch old_report.txt
touch current_data.log
touch temp_notes.txt

echo "Listing all .txt files found:"
find . -name "*.txt" -exec ls -l {} \;

# Clean up
rm old_report.txt current_data.log temp_notes.txt

Advanced Search Challenge

You need to find all .log files that are larger than 100KB and were modified in the last 3 days, then print their names.

Which combination of find options would achieve this?

Recap: Precision Searches

Great job! You've leveled up your text and file searching skills.

  • We explored Extended Regular Expressions (ERE) with grep -E, using +, ?, and | for more flexible pattern matching.
  • You learned to use advanced find criteria like -mtime, -atime, and -size.
  • We also covered combining these criteria with AND/OR logic and performing actions on found files using the powerful -exec option.

These tools are essential for efficient system administration and scripting!

Frequently asked questions

Is the “Advanced `grep` and `find` Patterns” lesson free?

Yes — the full text of “Advanced `grep` and `find` Patterns” is free to read here on the web, and the Linux Command Line Mastery course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Linux Command Line Mastery course, upgrade to CoddyKit PRO.

What will I learn in “Advanced `grep` and `find` Patterns”?

Utilize complex regex with `grep` and advanced criteria with `find` for precise searches. You practise Linux Command Line Mastery with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Linux Command Line Mastery?

No prior experience is required. Linux Command Line Mastery on CoddyKit is structured for beginners through advanced learners; this is — lesson 2 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Advanced `grep` and `find` Patterns” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Linux Command Line Mastery lesson?

Yes. Every Linux Command Line Mastery lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

  1. Mastering Regular Expressions (Regex)
  2. Advanced `grep` and `find` Patterns
  3. `xargs` for Command Chaining
  4. Stream Editing at Scale with sed and tr
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