Linux Commands
File Viewing & Editing
cat — Display file content
Prints entire file to terminal.
cat file.txt
- Useful for quick file checks or piping output.
less — View large files interactively
Scroll through files page by page.
less largefile.log
q→ Quit/text→ Search
Best for reading logs or big files.
head — View beginning of file
head file.txt
head -n 20 file.txt
Quickly inspect file headers.
tail — View end of file
tail file.txt
tail -n 50 file.txt
tail -f app.log
Common for live log monitoring.
nano — Simple text editor
nano file.txt
Ctrl + O→ SaveCtrl + X→ Exit
Beginner-friendly editing.
vim — Advanced text editor
vim file.txt
i→ Insert modeEsc→ Normal mode:wq→ Save & quit
Search & Find
find — Locate files (ec2)
find . -name "file.txt"
find /var/log -type f -name "*.log"
Precise but slower search.
grep — Search inside files
grep "error" app.log
grep -i "warning" app.log
grep -r "config" .
Essential for debugging & log analysis.
locate — Fast file search (ec2)
sudo apt-get update && sudo apt-get install plocate -y
locate service
sudo updatedb
Extremely fast (uses indexed database).
System Information
uname — System details
uname -a
top — Real-time processes
top
Press q to exit.
htop — Enhanced process viewer
htop
Easier navigation (if installed).
df — Disk space usage
df -h
du — Directory size
du -sh folder/
free — Memory usage
free -h
Process Management
ps — List processes
ps aux
kill — Stop process (by PID)
kill 1234
kill -9 1234
Use -9 only when necessary.
killall — Stop by name
killall chrome
bg — Resume in background
bg
fg — Bring to foreground
fg
Tips
Use manual pages
man grep
Combine commands (pipes)
cat file.txt | grep "error"
Monitor logs live
tail -f /var/log/syslog
