chmod (change file mode) - a change of the access mode is to the files in the operating systems of Unix, Linux and similar to them.
Notice. Here and farther a «file» understands in wide sense of this word is a file, catalogue, symbolic reference, socket and other.
Exists three groups of users of users: file (owner) proprietor, group to which a file (group) proprietor belongs and last (public)
Each from these three groups of users rights for ...