Linux Command Basics — Day 4: Search, Inspect, and Automate

Objectives

• Search for files with find
• Search inside files with grep and summarize
• Use xargs and –exec to batch edit files
• Write small scripts and make them executable

Materials

• Computers with terminal access

Activities

Mission: Search, Inspect, and Automate

Your Goal

Discover how to search for files and content, inspect multiple files quickly, and combine commands into small scripts to automate repetitive tasks. Learn by experimenting: run short experiments, capture command + output evidence, and explain what you discovered.

Duration

45 minutes

Allowed Tools (today)

find, grep, sort
head, tail, less, cat
xargs
echo, >, >>, |
bash # (small one-line scripts), chmod
pwd, ls, cd, cp, mv # (from earlier days)

find, grep, sort
head, tail, less, cat
xargs
echo, >, >>, |
bash # (small one-line scripts), chmod
pwd, ls, cd, cp, mv # (from earlier days)

Rules

• Work in pairs; switch Driver/Navigator every 8 minutes.
• Record each task with: command used, exact output (or screenshot), and 1–2 sentence explanation.
• Work inside your ~/mission-day2/ workspace created earlier.
• Use hint ladder only when stuck.

Starter checks

cd ~/mission-day2
ls -la
pwd

cd ~/mission-day2
ls -la
pwd

Record outputs for your notebook.

Tasks — Inquiry Challenges

Try each task, then record commands and outputs as evidence.

Task A — Locate the files

• Use find to list all .txt files under your workspace: find . -name "*.txt".
• Limit results to depth 2: find . -maxdepth 2 -name "*.txt".
• Evidence: commands and outputs; note how find differs from ls and when it’s useful.

Task B — Search inside files

• Use grep -n "pattern" to find lines containing a word (e.g., idea) across files: grep -n "idea" -R notes/.
• Use grep -i to ignore case and grep -r to search recursively.
• Evidence: the commands and matched lines with filenames.

Task C — Summarize and sort

• Combine commands to count matches: grep -r "idea" notes/ | wc -l.
• Produce a list of files containing matches and sort by count: grep -r "idea" notes/ | cut -d: -f1 | sort | uniq -c | sort -nr.
• Evidence: the pipeline commands and outputs; explain each step.

Task D — Batch edits with xargs

• Use find + xargs or -exec to perform an action on multiple files (e.g., append a line to every .txt).
• Safer example (use sh -c so redirection happens per-file):

find notes/ -name “*.txt” -print0 | xargs -0 -I {} sh -c ‘printf “checked %s\n” “$(date)” >> “$1″‘ — {}

• Evidence: before/after samples from one edited file.

Task E — Small script challenge

• Write a one-file script scripts/report.sh that prints a short report: number of .txt files and top 3 files with most matches for the word idea. Make it executable with chmod +x and run it.
• Example script body (one-file, portable — runs from the unit workspace):

  #!/bin/bash
  cd ~/mission-day2 || exit 1
  echo "TXT files: $(find . -name '*.txt' | wc -l)"
  echo "Top idea files:"
  grep -r "idea" notes/ | cut -d: -f1 | sort | uniq -c | sort -nr | head -n 3

  #!/bin/bash
  cd ~/mission-day2 || exit 1
  echo "TXT files: $(find . -name '*.txt' | wc -l)"
  echo "Top idea files:"
  grep -r "idea" notes/ | cut -d: -f1 | sort | uniq -c | sort -nr | head -n 3

• Evidence: script contents, chmod output (ls -l), and script run output.

Exit Ticket (short answers)

1. How does find differ from ls? Give one example.

2. What does xargs help you do?

3. Why might you prefer a small script over a long one-line pipeline?

4. How do you make a script executable?

Assessment (performance)

Students must submit a single text file mission-day4-evidence.txt in ~/mission-day2/ containing:

• For Tasks A–E: each task header, the commands you ran, captured outputs (or pasted snippets), and a one-line conclusion.
• Minimum: 5 command+output pairs demonstrating find, grep, a pipeline with sort/uniq, an xargs or -exec action, and a small executable script run.

Student Handout (printable)

Cheat-sheet (quick commands)

• Find files: find . -name "*.txt"
• Search text: grep -n "pattern" -R notes/
• Count matches: grep -r "pattern" notes/ | wc -l
• Summarize by file: grep -r "pattern" notes/ | cut -d: -f1 | sort | uniq -c | sort -nr
• Run command on many files: find . -name "*.txt" -print0 | xargs -0 -I {} <cmd> {}
• Small script: create file, add shebang #!/bin/bash, chmod +x file, ./file

Tasks (short)

• A: Use find to locate .txt files and note differences with ls.
• B: Use grep to search inside files for a keyword.
• C: Build a pipeline to count and rank files by matches.
• D: Use xargs or -exec to append a line to many files and show before/after for one file.
• E: Create a small executable script report.sh that summarizes workspace state and run it.

Submission: save mission-day4-evidence.txt in ~/mission-day2/ with your evidence.

Hint Ladder

Hint 1 — gentle

• find searches directories recursively; ls lists a directory.
• grep looks for text inside files; -n shows line numbers.
• xargs converts input lines into arguments for another command.

Hint 2 — specific

• Try: find . -name "*.txt"
• To count: grep -r "idea" notes/ | wc -l
• To append safely: find notes/ -name "*.txt" -print0 | xargs -0 -I {} sh -c 'printf "checked %s\n" "$(date)" >> "$1"' -- {}

Hint 3 — explicit commands

• find . -maxdepth 2 -name "*.txt"
• grep -n "idea" -R notes/
• grep -r "idea" notes/ | cut -d: -f1 | sort | uniq -c | sort -nr
• find notes/ -name "*.txt" -print0 | xargs -0 -I {} sh -c 'printf "checked %s\n" "$(date)" >> "$1"' -- {}

Differentiation

• Struggling students: focus on Tasks A and B only (finding + searching). Submit 3 command+output pairs.
• Advanced students: extend the script to accept a search term and output a CSV with filename,count.

Final check

Ensure ~/mission-day2/mission-day4-evidence.txt exists and contains all required evidence.

Exit Ticket

1) How does find differ from ls?

2) What does xargs help you do?

3) Why prefer a script over a long pipeline?

4) How do you make a script executable?