stat aaa.txt listed more detailed information
file view basic file types
mv aaa.txt abc.txt change the name
clear clear screen
SUMMARY cat output file
contents more output file (part, view the whole carriage)
10 tail aaa.dat row look after the contents of the file
tail -n 30 aaa.dat view line 30
tail -f -n 3 aaa.dat flush out the real-time 3-line back
ps to view system processes
ps -ef show All (-e show all processes -f show full output)
top
sudo apt-get install htop (htop Enter) more graphical image
df -h View Human disk space as Free Disk
du see those here are those subdirectories Usage Disk
du -h display when the unit k MG plus more intuitive