Calculate Unix file permissions with an interactive visual grid.
Command
chmod 755 filename
ls -l preview
-rwxr-xr-x 1 user group 0 Mar 7 12:00 filename
Unix permissions are represented as three octal digits (owner, group, others). Each digit is a sum of: Read (4), Write (2), Execute (1). For example, 755 means owner can read/write/execute, while group and others can read/execute.