Practice Use drills for recall and labs for real operating judgment.

LAB-TEXT-02 - The Surgeon's Knife: grep

Use grep to find matching lines, ignore noise, and search recursively through realistic text samples.

TXT Text Processing

The Surgeon's Knife: grep

Use grep to find matching lines, ignore noise, and search recursively through realistic text samples.

35 min BEGINNER LINUX Curriculum-reviewed
Prerequisites
Lab LAB-TEXT-01 - The Unix Philosophy: Pipes & Redirection
Success criteria
  • Use grep to find matching lines, ignore noise, and search recursively through realistic text samples.
  • Repeat the workflow without copy-paste or step-by-step prompting.
Safety notes
  • Practice recursive searches in known folders first so you understand the scope before searching larger trees.

Part A: The Field Guide

What This Lab Is Really About

grep is one of the simplest and most useful ways to turn a large block of text into a short answer.

You will use it to:

  • find matching lines
  • ignore case when needed
  • remove lines you do not want
  • search through multiple files

Command Reference

Common grep patterns

grep “WARN” app.log grep -i “warning” app.log grep -v ”^#” config.conf grep -r “timezone” configs/

Part B: The Drill Deck

Terminal required: work inside a disposable text-practice folder.

G
Guided Step by step - type exactly this and compare the result
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Exercise G1: Create a Small Log File

  1. Create a workspace:
mkdir -p "$HOME/grep_lab"
cd "$HOME/grep_lab"
  1. Create sample log content:
printf "INFO boot\nWARN disk almost full\nERROR service stopped\nINFO done\n" > app.log
  1. Search for one word:
grep "WARN" app.log

Exercise G2: Ignore Case

  1. Add one lowercase warning:
echo "warning cache cold" >> app.log
  1. Compare these two commands:
grep "warning" app.log
grep -i "warning" app.log
  1. Confirm why -i matters.

Exercise G3: Remove Comment Lines

  1. Create a small config file:
printf "# comment\nPort 22\n# disabled\nPermitRootLogin no\n" > config.conf
  1. Remove comment lines:
grep -v "^#" config.conf
  1. Confirm that only the active-looking settings remain.
S
Solo Task described, hints available - figure it out
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Exercise S1: Search a Folder Recursively

  1. Create a subfolder:
mkdir -p configs
cp config.conf configs/ssh.conf
echo "timezone=UTC" > configs/app.conf
  1. Search the folder:
grep -r "timezone" configs
  1. Confirm that grep shows both the filename and the matching line.

Exercise S2: Use grep in a Pipe

  1. Run:
cat app.log | grep "INFO"
  1. Confirm that grep works as both a direct file search and a pipeline filter.
M
Mission Real scenario - no hints, combine multiple skills
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Mission M1: Show Only the Active Settings

Create a file named server.conf with this content:

# sample server config

Listen 8080
# Debug true
Mode production

Now write a pipeline that removes:

  1. lines starting with #
  2. lines that are completely blank

You should end up with only the active settings shown on screen.