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LinuxPapers.org: File Permissions in Unix and Linux

Apr 14, 2000, 13:31 (2 Talkback[s])
(Other stories by Piero Baudino)

[ Thanks to newsmaster@linuxpapers.org for this link. ]

"This article describes the basic notions around file permissions in Unix and GNU/Linux, giving the reader the knowledge to use them effectively"

"In every computer that has a Unix-like operative system, such as GNU/Linux, many different users are able to access the system. In order to guarantee the security and the privacy of each user's data, the operative system is equipped with mechanisms that allow us to manage the permissions associated with every element in the filesystem, the files and directories. For each of these elements there is an owner and a group: the owner is the user that the file or directory belongs to, and the group is a particular group of users that in general are able to access that file or directory."

"The file permissions for test_file, are shown by the first 10 symbols in the output from ls. The first symbol, in the case of files, is always -, while the remaining nine symbols describe the permissions that are associated with the file. Those nine symbols are divided into three groups of three (from left to right):

  • permissions for the user that owns the file
  • permissions for the users in the file's group
  • permissions for all other users in the system"
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