touch file.txt
ls -l file.txt
chmod g+w file.txt # add write permission to group
ls -l file.txt
chmod a+w file.txt # add write permission to all users
ls -l file.txt
chmod a-w file.txt # remove write permission from all users
ls -l file.txt
chown guest file.txt
ls -l file.txt
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX