CLI Mastery Training

Deliberate practice curriculum for terminal mastery.

Training Philosophy

Type commands by hand - no copy-paste during practice
Eyes-closed drills - build muscle memory
Observation → Immediate reproduction - see pattern, type it
Infrastructure context - all exercises use real domus-* data

Resources

Resource	URL
regex101.com	regex101.com/ - Test regex with explanation
explainshell.com	explainshell.com/ - Break down complex commands
shellcheck.net	www.shellcheck.net/ - Lint bash scripts

Resource

URL

regex101.com

regex101.com/ - Test regex with explanation

explainshell.com

explainshell.com/ - Break down complex commands

shellcheck.net

www.shellcheck.net/ - Lint bash scripts

Skill Levels

Level	Indicators	Status
Beginner	GUI-dependent, copies commands, afraid of terminal	[x] PASSED
Intermediate	Terminal-first, pipelines, find+grep, heredocs	[x] CURRENT
Advanced	Process substitution, FIFOs, signals, awk/sed without docs	[ ] IN TRAINING
Expert	Designs workflows, portable scripts, teaches others	[ ] FUTURE

Level

Indicators

Status

Beginner

GUI-dependent, copies commands, afraid of terminal

[x] PASSED

Intermediate

Terminal-first, pipelines, find+grep, heredocs

[x] CURRENT

Advanced

Process substitution, FIFOs, signals, awk/sed without docs

[ ] IN TRAINING

Expert

Designs workflows, portable scripts, teaches others

[ ] FUTURE

Module 1: Process Substitution

Concept

<(command) creates a file descriptor (/dev/fd/63) containing command output.

Pattern

diff <(command1) <(command2)

Exercises

Exercise 1.1: Compare attributes across repos

diff <(grep -E "^    [a-z]" ~/atelier/_bibliotheca/domus-infra-ops/docs/asciidoc/antora.yml | sort) \
     <(grep -E "^    [a-z]" ~/atelier/_bibliotheca/domus-captures/docs/antora.yml | sort)

Expected: No output (attributes synchronized)

Exercise 1.2: Compare DNS records from two servers

diff <(dig @10.50.1.90 inside.domusdigitalis.dev AXFR | sort) \
     <(dig @10.50.1.91 inside.domusdigitalis.dev AXFR | sort)

Exercise 1.3: Compare package lists

diff <(pacman -Qq | sort) <(cat ~/.config/packages/base.txt | sort)

Exercise 1.4: Compare running processes across hosts

diff <(ssh kvm-01 "ps aux --no-headers | awk '{print \$11}' | sort -u") \
     <(ssh kvm-02 "ps aux --no-headers | awk '{print \$11}' | sort -u")

Completion Criteria

[ ] Type diff <() <() without reference [ ] Use for comparing remote vs local files [ ] Use for comparing git branches [ ] Explain why it’s better than temp files

Module 2: comm - Set Operations

Concept

Compares two sorted files, outputs 3 columns:

| Column | Indent | Meaning | |--------|--------|---------| | 1 | None | Only in file 1 | | 2 | One tab | Only in file 2 | | 3 | Two tabs | In both files |

| Flag | Effect | |------|--------| | -1 | Suppress column 1 | | -2 | Suppress column 2 | | -3 | Suppress column 3 (most common) | | -12 | Show only common lines | | -23 | Show only file1-unique | | -13 | Show only file2-unique |

Exercises

Exercise 2.1: Find files unique to each repo

comm -3 \
  <(find ~/atelier/_bibliotheca/domus-infra-ops -name "*.adoc" -printf "%f\n" | sort -u) \
  <(find ~/atelier/_bibliotheca/domus-captures -name "*.adoc" -printf "%f\n" | sort -u) \
  | head -20

Exercise 2.2: Count unique files with awk

comm -3 \
  <(find ~/atelier/_bibliotheca/domus-infra-ops -name "*.adoc" -printf "%f\n" | sort -u) \
  <(find ~/atelier/_bibliotheca/domus-captures -name "*.adoc" -printf "%f\n" | sort -u) \
  | awk '/^\t/{r++} /^[^\t]/{l++} END{print "infra-ops only:", l, "\ncaptures only:", r}'

Expected: infra-ops only: 275, captures only: 437

Exercise 2.3: Find common files only

comm -12 \
  <(find ~/atelier/_bibliotheca/domus-infra-ops -name "*.adoc" -printf "%f\n" | sort -u) \
  <(find ~/atelier/_bibliotheca/domus-captures -name "*.adoc" -printf "%f\n" | sort -u) \
  | wc -l

awk Pattern Breakdown

| Pattern | Meaning | |---------|---------| | /^\t/ | Line starts with tab | | /^[\t]/ | Line starts with non-tab | | {r++} | Increment counter r | | END{print} | Print after all lines |

Completion Criteria

[ ] Explain 3-column output [ ] Use -3 flag correctly [ ] Combine with awk for counting [ ] Use -12 for intersection

Module 3: Git Log Ranges

Concept

A..B means "commits reachable from B but NOT from A"

Patterns

# Last N commits
git log HEAD~1..HEAD    # 1 commit
git log HEAD~2..HEAD    # 2 commits
git log HEAD~5..HEAD    # 5 commits

# Branch comparison
git log main..feature   # Commits on feature not on main
git log feature..main   # Commits on main not on feature

# With formatting
git log --oneline HEAD~5..HEAD

Exercises

Exercise 3.1: View last 3 commits

git log --oneline HEAD~3..HEAD

Exercise 3.2: View commits with full message

git log HEAD~2..HEAD | cat

Exercise 3.3: Compare branches

git log --oneline main..HEAD  # What's on current branch not on main

Completion Criteria

[ ] Explain A..B semantics [ ] Use HEAD~N notation fluently [ ] Compare branches with ranges

Module 4: Git Reflog

Concept

Every HEAD movement is recorded. Safety net for ~90 days.

Patterns

# View recent movements
git reflog | head -10

# Format
# 45163b7 HEAD@{0}: commit: message
# a4a04bf HEAD@{1}: commit: message

# Recovery after bad reset
git reset --hard HEAD~5    # Oops!
git reflog                 # Find lost commit
git reset --hard HEAD@{1}  # Recover

Exercises

Exercise 4.1: View your reflog

git reflog | head -15

Exercise 4.2: Find a specific action

git reflog | grep -i "reset\|rebase\|checkout"

Completion Criteria

[ ] Explain reflog purpose [ ] Use HEAD@{N} syntax [ ] Recover from bad reset

Module 5: find Patterns

Core Syntax

find <path> -type <f|d> -name "pattern" -exec <cmd> {} \;

Exercises

Exercise 5.1: Find by name with regex OR

find ~/atelier/_bibliotheca/Principia/ -type f \( -name "*.adoc" -o -name "*.md" \) | head -10

Exercise 5.2: Find and grep

find ~/atelier/_bibliotheca -name "*.adoc" -exec grep -l "LUKS" {} \; 2>/dev/null

Exercise 5.3: Find with printf (for sort/comm)

find ~/atelier/_bibliotheca/domus-captures -name "*.adoc" -printf "%f\n" | sort -u | head -10

Exercise 5.4: Find by time

find ~/atelier/_bibliotheca -name "*.adoc" -mtime -1  # Modified in last 24h

Completion Criteria

[ ] Use -type f vs -type d [ ] Use -name with globs [ ] Use -exec with {} and \; [ ] Use -printf for custom output

Module 6: Regex (regex101.com)

Flavors

| Context | Flavor | Notes | |---------|--------|-------| | grep | BRE | Escape +, ?, \|, () | | grep -E | ERE | No escaping needed | | grep -P | PCRE | Full Perl regex | | awk | ERE | Extended by default | | sed | BRE | Use -E for ERE |

Exercises (Use regex101.com)

Exercise 6.1: Match IPv4 addresses

Pattern: \b([0-9]{1,3}\.){3}[0-9]{1,3}\b
Test: "Server at 10.50.1.90 responded"

Exercise 6.2: Match MAC addresses

Pattern: ([0-9a-fA-F]{2}:){5}[0-9a-fA-F]{2}
Test: "MAC 14:F6:D8:7B:31:80 registered"

Exercise 6.3: BRE vs ERE escaping

# BRE (requires escaping)
echo "test123" | grep 'test\(123\)'

# ERE (no escaping)
echo "test123" | grep -E 'test(123)'

Practice Workflow

Open regex101.com/
Select flavor (PCRE for testing, then adapt)
Enter pattern and test strings
Read explanation on right panel
Port to grep/awk/sed

Completion Criteria

[ ] Explain BRE vs ERE vs PCRE [ ] Write IP address regex [ ] Write MAC address regex [ ] Use regex101.com effectively

Module 7: awk Fundamentals

Core Patterns

# Field extraction
awk '{print $1, $3}' file

# Pattern matching
awk '/pattern/ {print $0}' file

# Field separator
awk -F: '{print $1}' /etc/passwd

# Counters
awk '{count++} END {print count}' file

# Conditionals
awk '$3 > 100 {print $1}' file

Exercises

Exercise 7.1: Extract usernames from passwd

awk -F: '{print $1}' /etc/passwd | head -10

Exercise 7.2: Count lines matching pattern

awk '/LUKS/ {count++} END {print count}' ~/atelier/_bibliotheca/domus-captures/docs/modules/ROOT/**/*.adoc

Exercise 7.3: Tab-detection pattern (from comm)

# From Session 5
awk '/^\t/{r++} /^[^\t]/{l++} END{print "left:", l, "right:", r}'

Completion Criteria

[ ] Use -F for field separator [ ] Use pattern {action} syntax [ ] Use END\{\} for totals [ ] Write counters with ++

Module 8: jq for JSON

Core Patterns

# Pretty print
cat file.json | jq .

# Extract field
jq '.name' file.json

# Array access
jq '.[0]' file.json
jq '.items[0].name' file.json

# Filter
jq '.[] | select(.status == "active")' file.json

Exercises

Exercise 8.1: Parse netapi JSON output

netapi ise get-endpoints -f json | jq '.SearchResult.resources[].name' | head -5

Exercise 8.2: Extract specific fields

netapi monad pipelines -f json | jq '.[] | {name: .name, status: .status}'

Completion Criteria

[ ] Navigate nested objects with . [ ] Access arrays with [] [ ] Use select() for filtering [ ] Use | for chaining

Module 9: xargs Patterns

Core Patterns

# Basic
find . -name "*.txt" | xargs wc -l

# With placeholder
find . -name "*.txt" | xargs -I{} cp {} /backup/

# Null-delimited (safe for spaces)
find . -name "*.txt" -print0 | xargs -0 wc -l

# Parallel
find . -name "*.txt" | xargs -P4 -I{} process {}

Exercises

Exercise 9.1: Count lines in all .adoc files

find ~/atelier/_bibliotheca/domus-captures -name "*.adoc" | xargs wc -l | tail -1

Exercise 9.2: Safe handling with -print0

find ~/atelier/_bibliotheca -name "*.adoc" -print0 | xargs -0 grep -l "LUKS"

Completion Criteria

[ ] Use -I{} for placeholder [ ] Use -print0 and -0 together [ ] Use -P for parallel execution

Module 10: sort - Ordering Data

Core Patterns

# Alphabetic sort (default)
sort file.txt

# Numeric sort
sort -n file.txt

# Reverse
sort -r file.txt

# Unique only
sort -u file.txt

# By field (tab-delimited)
sort -t$'\t' -k2 file.txt

# By field (colon-delimited)
sort -t: -k3 -n /etc/passwd

# Human-readable numbers (1K, 2M, 3G)
du -h | sort -h

Exercises

Exercise 10.1: Sort passwd by UID

sort -t: -k3 -n /etc/passwd | head -10

Exercise 10.2: Sort files by size

ls -lS | head -10  # ls has -S flag
du -h * | sort -h  # sort human-readable

Exercise 10.3: Unique sorted output for comm

find . -name "*.adoc" -printf "%f\n" | sort -u

Completion Criteria

[ ] Use -n for numeric [ ] Use -t and -k for field sorting [ ] Use -u for unique [ ] Use -h for human-readable sizes

Module 11: cut - Field Extraction

Core Patterns

# By delimiter and field
cut -d: -f1 /etc/passwd

# Multiple fields
cut -d: -f1,3,7 /etc/passwd

# Field range
cut -d: -f1-3 /etc/passwd

# By character position
cut -c1-10 file.txt

# By byte position
cut -b1-10 file.txt

Exercises

Exercise 11.1: Extract usernames

cut -d: -f1 /etc/passwd | head -10

Exercise 11.2: Extract username and shell

cut -d: -f1,7 /etc/passwd | head -10

Exercise 11.3: Extract first 20 characters of each line

head /etc/passwd | cut -c1-20

Exercise 11.4: cut vs awk

# Equivalent operations
cut -d: -f1 /etc/passwd
awk -F: '{print $1}' /etc/passwd

# When to use each:
# cut: Simple field extraction, faster
# awk: Complex logic, calculations, patterns

Completion Criteria

[ ] Use -d for delimiter [ ] Use -f for fields [ ] Use -c for characters [ ] Know when to use cut vs awk

Module 12: tr - Translate Characters

Core Patterns

# Replace characters
echo "hello" | tr 'a-z' 'A-Z'  # HELLO

# Delete characters
echo "hello123" | tr -d '0-9'  # hello

# Squeeze repeated characters
echo "helllo" | tr -s 'l'      # helo

# Complement (delete everything NOT in set)
echo "hello123" | tr -cd '0-9' # 123

Exercises

Exercise 12.1: Uppercase

echo "infrastructure" | tr 'a-z' 'A-Z'

Exercise 12.2: Remove digits

echo "vault-01.inside.domusdigitalis.dev" | tr -d '0-9'

Exercise 12.3: Convert spaces to newlines

echo "one two three" | tr ' ' '\n'

Exercise 12.4: Squeeze multiple spaces

echo "too    many    spaces" | tr -s ' '

Completion Criteria

[ ] Use character ranges a-z [ ] Use -d to delete [ ] Use -s to squeeze [ ] Use -c for complement

Module 13: head/tail - File Slicing

Core Patterns

# First/last N lines
head -10 file.txt
tail -10 file.txt

# First/last N bytes
head -c 100 file.txt

# All BUT last N lines
head -n -5 file.txt

# All FROM line N onward
tail -n +5 file.txt

# Follow file (live)
tail -f /var/log/syslog

# Follow with retry
tail -F /var/log/syslog

Exercises

Exercise 13.1: Lines 10-20 of a file

head -20 file.txt | tail -11
# OR
sed -n '10,20p' file.txt
# OR
awk 'NR>=10 && NR<=20' file.txt

Exercise 13.2: Skip header line

tail -n +2 /etc/passwd | head -5

Exercise 13.3: Last 5 commits

git log --oneline | head -5

# Lines, words, bytes
wc file.txt

# Lines only
wc -l file.txt

# Words only
wc -w file.txt

# Characters
wc -c file.txt

# Multiple files
wc -l *.txt

Exercises

Exercise 14.1: Count .adoc files

find ~/atelier/_bibliotheca/domus-captures -name "*.adoc" | wc -l

Exercise 14.2: Total lines in all files

find ~/atelier/_bibliotheca/domus-captures -name "*.adoc" -exec cat {} + | wc -l

Exercise 14.3: Lines per file, sorted

find . -name "*.adoc" -exec wc -l {} + | sort -n | tail -10

# Remove adjacent duplicates (MUST sort first!)
sort file.txt | uniq

# Count occurrences
sort file.txt | uniq -c

# Only duplicates
sort file.txt | uniq -d

# Only unique (non-duplicated)
sort file.txt | uniq -u

# Ignore case
sort file.txt | uniq -i

Exercises

Exercise 15.1: Count file extensions

find ~/atelier/_bibliotheca -type f | sed 's/.*\.//' | sort | uniq -c | sort -rn | head -10

Exercise 15.2: Find duplicate filenames

find ~/atelier/_bibliotheca -name "*.adoc" -printf "%f\n" | sort | uniq -d

# Write to file AND stdout
command | tee output.txt

# Append instead of overwrite
command | tee -a output.txt

# Write to multiple files
command | tee file1.txt file2.txt

# With sudo (common pattern)
echo "config" | sudo tee /etc/file.conf

Exercises

Exercise 16.1: Save and display

git log --oneline HEAD~5..HEAD | tee /tmp/recent-commits.txt

Exercise 16.2: Write to privileged file

echo "new line" | sudo tee -a /etc/hosts

# Find most common words
cat file.txt | tr ' ' '\n' | sort | uniq -c | sort -rn | head -10

# Find large files
find . -type f -exec du -h {} + | sort -h | tail -10

# Process log files
cat /var/log/syslog | grep ERROR | cut -d' ' -f1-3 | sort | uniq -c

# Extract IPs from log
grep -oE '([0-9]{1,3}\.){3}[0-9]{1,3}' /var/log/auth.log | sort | uniq -c | sort -rn

Infrastructure Drills

Drill 17.1: Find most common file extensions in domus-*

find ~/atelier/_bibliotheca -type f | sed 's/.*\.//' | sort | uniq -c | sort -rn | head -10

Drill 17.2: Count lines per repo

for repo in domus-captures domus-infra-ops domus-ise-linux; do
  echo -n "$repo: "
  find ~/atelier/_bibliotheca/$repo -name "*.adoc" -exec cat {} + 2>/dev/null | wc -l
done

Drill 17.3: Compare repo sizes

du -sh ~/atelier/_bibliotheca/domus-* | sort -h

Module	Exercise	Status
1	1.1	[x] Completed - attributes comparison
2	2.1	[x] Completed - unique files
2	2.2	[x] Completed - awk counting (275/437)
3	3.1	[x] Completed - git log ranges
4	4.1	[x] Completed - reflog viewing

Notes:

Eyes-closed typing drill attempted
Typos caught: /^t/ → /^\t/, /^{\t]/ → /^[\t]/
Process substitution syntax internalized

Quick Reference Card

# Process substitution
diff <(cmd1) <(cmd2)

# comm (requires sorted input)
comm -3 <(sort file1) <(sort file2)

# Git ranges
git log HEAD~N..HEAD
git reflog | head

# find + grep
find . -name "*.adoc" -exec grep -l "pattern" {} \;

# awk counting
awk '/pattern/{c++} END{print c}'

# jq
jq '.field' | jq '.[] | select(.x == "y")'

# xargs safe
find . -print0 | xargs -0 cmd