In Unixlike operating systems, the chmod command is used to change the access mode of a file The name is an abbreviation of change mode chmod R or *page Numerical Shorthand Another way to use chmod is to provide the permissions you wish to give to the owner, group, and others as a threedigit number The leftmost digit represents the permissions for the ownerThe chmod command uses a threedigit code as an argument The three digits of the chmod code setpermissions for these groups in this order Owner (you) Group (a group of other users that you set up) World (anyone else browsing around on thefile system)
Understanding Unix Permissions And File Types Unix Linux Stack Exchange
Chmod numbers in unix