File and Directory Permissions

File and directory permissions are a fundamental part of Linux security, controlling who can read, write, and execute a file or directory.

The `ls -l` Output

When you run `ls -l`, the first column of the output shows the permissions.

    -rw-r--r-- 1 user group 4.0K May 15 10:00 file.txt
    drwxr-xr-x 2 user group 4.0K May 15 10:00 directory

The first character indicates the file type (`-` for a regular file, `d` for a directory). The following nine characters are the permissions, in three sets of three.

Understanding Permission Sets

Characters	Permissions For
`rwx`	Owner (The user who owns the file)
`r--`	Group (Members of the file's group)
`r--`	Others (All other users)

The Permissions

Character	Permission
`r`	Read: Permission to read a file or list a directory's contents.
`w`	Write: Permission to modify a file or create/delete files in a directory.
`x`	Execute: Permission to run a file (if it's a script or program) or enter a directory.