File Ownership

• chown → Change ownership
• chgrp → Change group

Access Control List (ACL)

• setfacl → Set file ACL
• getfacl → Get file ACL

Add Permission to User

setfacl -m u:user:rwx /path/to/file
setfacl -m g:group:rw /path/to/file

Recursive Inheritance from Folder

setfacl -R -m entry /path/to/dir

Remove Specific ACL Entry

setfacl -x u:user /path/to/file

Remove All ACL Entries

setfacl -b /path/to/file

Check ACL

ls -ltr

Example output:

-rw-rw-r--+

Help Commands

• whatis command
• command --help
• man command

Add Text to a File

echo "my text" > myfile    # Overwrite
cat myfile                 # Read the text
echo "hello" >> myfile     # Append

Input and Output Redirects
3 Redirect Types

• stdin → 0 → < or << → Feeding file content to a command
• stdout → 1 → > or >>
• stderr → 2 → 2> or 2>> → Write error output to a file

tee Command

• tee → Output + Save

echo "test" | tee myfile
tee -a file  # Append