File permissions

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The file permission is a term from the computer , on the basis of a system administrator in many operating systems, different access rights of users or groups of users to files or directories can give.

In this way, for example, a large number of different access rights can be distributed to users and / or user groups in a network . A user can thus also be assigned to several user groups without it being ruled out that he receives his own user access within which he can freely decide about file permissions.

Classic access rights for files and folders that can be combined with one another are, for example, read , write , read / execute , change and full access .

Implementations

DOS and Microsoft Windows 9x

Under DOS and old Microsoft Windows versions there are no file permissions because they are not multi-user systems. The command line attribtool only allows the user to change the file attributes Archive , Hidden / System and Read- only .

Microsoft Windows NT

Under Windows NT version 3.5 or higher , thanks to the use of the NTFS file system, there is the option of using extended file access rights .

Unix and its derivatives

Unix as a classic multi-user operating system has had file rights since the first version. Since Unix-V4 (1974) these have been divided into the three user classes owner ( user ), group ( group ) and “all others” ( others ). For each file and each folder, the rights to read , write and execute can be assigned independently of each other for each of these classes (see commands for user and rights management ). In addition to these file rights, there are also the three extended file rights bits Set user identity , Set group identity and the sticky bit .

Newer versions of many Unix derivatives in particular also support access control lists ( ACLs ) if the file system allows it .

VMS and OpenVMS

In the VMS or OpenVMS operating system from DEC, there is not only the classic Unix file rights read / write / execute but also the delete right . With the DIGITAL Command Language , the file permissions for file are set with the instruction 

SET PROTECTION=(S:x,G:x,O:x,W:x) "file"

assigned, xeach standing for a combination of RWED ( Read , Write , Execute , Delete ). The user group S stands for system , Gfor group , Ofor owner and Wfor world (all other users). The permissions for a file are set with the command 

SHOW PROTECTION "file"

displayed.