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 access can be appointed: reading (read), record (write) and implementations (execute) which mark r briefly, w and e accordingly. If a group owns that or by other right, character, proper this right, belongs, a hyphen belongs otherwise.

Example. That owns rights on reading and record reflected so: rw-

Right for all three groups of users written down together in the that sequence of which they are indicated higher.

Example. File proprietor and group to which he belongs own all of rights, and the last own rights on reading and implementation, chmod is reflected so: rwxrwxr-x

Except for the character format of record of rights for access, described higher there is also a numerical format of record of rights for access essence of which in more compact record is right as a visimkovogo number. For this purpose it is needed in the character format of letter to substitute by unit, and hyphens - on a zero; got a binary number needs to be presented in a visimkovomu format - it and there will be chmod in a numerical format.

Example. chmod is set so: rwxrwxr-x replaceable on 11111101, got binary commutable visimkovim, will get the numerical format of record of chmod - 775

For the best understanding suggest to take advantage of form of transformation of usual us form of record of chmod in a numerical format, and, opposite.