25 Bash One-Liners That Will Make You Look Like a Pro
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25 Bash One-Liners That Will Make You Look Like a Pro

Publish Date: Mar 3
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The difference between a beginner and an expert Bash user is efficiency. The best Bash users don’t waste time typing long-winded commands—they use powerful one-liners to get things done in seconds.

In this guide, you’ll find 25 practical Bash one-liners that solve real-world problems. Whether you’re managing files, troubleshooting servers, or processing logs, these commands will help you work smarter, not harder.

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1. File and Directory Management

1. Quickly backup a file before editing 

cp file.txt{,.bak}
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Why it’s useful: Ever made a change and regretted it? This creates file.txt.bak instantly before editing.

2. Find and delete files older than 30 days 

find /path/to/dir -type f -mtime +30 -delete
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Real-world use case: Useful for log rotation or cleaning up old backups.

3. Rename all .txt files to .log 

for file in *.txt; do mv "$file" "${file%.txt}.log"; done
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Why it matters: Automates batch renaming instead of renaming files manually.

4. Create a directory structure in one command 

mkdir -p project/{src,bin,logs,config}
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How this helps: Perfect for setting up project directories quickly.

5. Find the largest files in a directory 

du -ah /path/to/dir | sort -rh | head -10
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When to use: Great for troubleshooting full disks in Linux servers.

2. Text Processing & Log Analysis

6. Count occurrences of "error" in a log file 

grep -o "error" logfile.txt | wc -l
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Real-world scenario: Helps quickly check for recurring errors in server logs.

7. Extract only email addresses from a file 

grep -E -o "[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,6}" file.txt
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Why it’s useful: Saves time when scraping contact emails from logs or files.

8. Convert all text to lowercase 

tr '[:upper:]' '[:lower:]' < file.txt
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Why you need it: Useful when processing case-insensitive data.

9. Find duplicate lines in a file 

sort file.txt | uniq -d
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When to use it: Helps detect repeated log entries.

10. Extract specific columns from a CSV file 

awk -F, '{print $1, $3}' data.csv
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Real-world application: If you have a CSV file with 5+ columns and only need two, this keeps it clean.

3. System Monitoring & Debugging

11. Check CPU usage per process 

ps -eo pid,comm,%cpu --sort=-%cpu | head -10
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Why it matters: Helps troubleshoot high CPU usage.

12. Monitor memory usage in real-time 

watch -n 1 free -m
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Real-world scenario: Essential for diagnosing out-of-memory issues.

13. Check which process is using a specific port 

netstat -tulnp | grep ":80"
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When to use: Useful when Apache or Nginx isn’t starting due to port conflicts.

14. Find recently modified files 

find . -type f -mtime -1
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Why it helps: Instantly detect recently changed files in case of a suspected security issue.

15. View last 100 lines of a log file in real-time 

tail -n 100 -f /var/log/syslog
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Why it’s critical: Helps catch system errors as they happen.

4. Automation & Scheduling

16. Run a command every 10 seconds 

watch -n 10 "date"
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Real-world scenario: Useful for monitoring time-sensitive tasks.

17. Automatically restart a service if it crashes 

while true; do systemctl is-active --quiet myservice || systemctl restart myservice; sleep 60; done
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Why it’s powerful: Automates uptime monitoring.

18. Run a script at 3 AM daily 

echo "0 3 * * * /path/to/script.sh" | crontab -
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Use case: Perfect for backup or maintenance scripts.

5. Networking & Security

21. Check your public IP address 

curl -s https://ifconfig.me
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22. Test if a website is reachable 

curl -Is https://example.com | head -n 1
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23. Scan open ports on a remote server 

nmap -p 1-65535 example.com
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24. Block an IP address using iptables 

iptables -A INPUT -s 192.168.1.100 -j DROP
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25. Find all failed SSH login attempts 

grep "Failed password" /var/log/auth.log
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Final Thoughts: From One-Liners to Mastering Bash

These Bash one-liners are just a glimpse of what’s possible. A true Bash expert knows when and why to use them effectively.

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