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What does "777" mean in *nix filesystems?

In a *nix systems, you are able to change the actual permissions by using a command line command. The problem with this is the fact that you don't have a nice GUI like Windows does to click and choose what permissions goes where.

The "777" actually represents two things. Each digit in the number represents a bit string for the actual permissions (see below), but also each character means something. The sevens are broken down as follows:

  1. Digit 1 = user
  2. Digit 2 = group
  3. Digit 3 = world

Depending on what each are set to, the user/group/world will have the permissions that it was set to.

Now, what do each piece of the bit string mean? A "1" means that the value is allowed and a "0" means that it is not allowed. So, starting from left to right:

  1. Digit 1 = Read
  2. Digit 2 = Write
  3. Digit 3 = Execute

So, if you want a user to have read permissions only on the file, you would have a binary string of "100" which is 4, so the file permission would be 4xx (where xx doesn't matter because we are only talking about user).

The lazy man's file permission is "777" because you are essentially everyone access to do whatever they want to do with the file.

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