Ubuntu-L3-Sergeant

Text Processing & Streams

1. echo — Print text or variables

   echo "Hello Ubuntu"

2. wc — Count lines, words, characters

   wc file.txt

3. sort — Sort lines in a file

   sort names.txt

4. uniq — Remove duplicate lines

   uniq file.txt

5. cut — Extract columns from text

   cut -d',' -f1 data.csv

6. tr — Translate or delete characters

   tr 'a-z' 'A-Z'

7. awk — Pattern scanning and processing

   awk '{print $1}' file.txt

8. sed — Stream editor for text replacement

   sed 's/error/warning/g' file.txt

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Environment & Shell Control

1. env — Show environment variables

   env

2. export — Set environment variables

   export APP_ENV=production

3. source — Reload shell configuration

   source ~/.bashrc

4. which — Locate a command binary

   which python

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Disk Usage & Filesystems

1. du -h — Directory size usage

   du -h --max-depth=1

2. statx — Extended file statistics (newer Ubuntu)

   statx file.txt

3. file — Detect file type

   file unknown.bin

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Scheduling & Automation

1. crontab — Schedule jobs

   crontab -e

2. at — Run commands at a specific time

   echo "backup.sh" | at 22:00

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Services & Systemd

1. systemctl status — Check service status

   systemctl status ssh

2. systemctl start — Start a service

   sudo systemctl start nginx

3. systemctl enable — Start service at boot

   sudo systemctl enable docker

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Networking & Sessions

1. ss — Inspect open ports and sockets

   ss -tuln

2. who — Logged-in users

   who

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Power & Session Management

1. uptime — System running time

   uptime

2. shutdown — Power off or reboot

   sudo shutdown now

3. reboot — Restart system

   sudo reboot

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