Linux command line skills

 If you're looking to level up your Linux command line skills, here’s a curated list of advanced Linux commands, tools, and techniques, categorized by functionality:

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🔍 File and Text Processing

1. awk

   awk '{print $2, $1}' file.txt
   

   • Powerful for pattern scanning and processing.

2. sed

   sed -E 's/([0-9]{3})/\1-/' file.txt
   

   • Stream editor for modifying files or inputs inline.

3. xargs

   find . -name '*.log' | xargs grep 'ERROR'
   

   • Converts input from stdin into arguments to a command.

4. cut, paste, tr, sort, uniq, tee

   cut -d':' -f1 /etc/passwd | sort | uniq
   

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🧠 System Monitoring and Performance

1. htop / atop / glances

   • Interactive process viewers.

2. iotop

   • Shows disk I/O by process.

3. strace

   strace -p <PID>
   

   • Traces system calls of a process.

4. lsof

   lsof -i :80
   

   • Lists open files and ports.

5. watch

   watch -n 2 df -h
   

   • Repeats a command at intervals.

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📁 Disk & Filesystem Tools

1. ncdu

   • Visual disk usage analysis.

2. df, du

   du -sh * | sort -h
   

3. mount, umount, lsblk, blkid

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🧰 Networking & Sockets

1. netstat / ss

   ss -tuln
   

2. nmap

   nmap -sV 192.168.1.1
   

3. tcpdump

   tcpdump -i eth0 port 80
   

4. curl, wget, nc (netcat)

   curl -I https://example.com
   nc -vz google.com 80
   

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🔐 Permissions, Security, & Users

1. chmod, chown, setfacl, getfacl

2. sudo, visudo

3. usermod, groupadd, passwd

4. ssh, scp, rsync

   rsync -avz /local/dir/ user@host:/remote/dir/
   

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🔄 Automation and Scripting

1. cron, at

   crontab -e
   

2. Shell scripting:

   for i in *.log; do gzip "$i"; done
   

3. trap, set -euo pipefail for robust scripts.

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📦 Package Management

• Debian/Ubuntu: apt, dpkg

• Red Hat/CentOS: yum, dnf, rpm

• Arch: pacman

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🧠 Cool Pro Tips

1. Brace expansion:

   mkdir -p project/{src,bin,doc}
   

2. Process substitution:

   diff <(ls dir1) <(ls dir2)
   

3. Command chaining:

   cmd1 && cmd2 || echo "cmd1 failed"
   

4. Parallel execution with & and wait:

   cmd1 & cmd2 & wait
   

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If you want a focused guide (e.g. for networking, performance tuning, or scripting), just let me know!