More Information About Modes

There are three types of permissions for a file or directory: read, write, and execute.

File

Directory

Each file has three different access permissions

The output of thels -al command lists all the permissions. There are ten characters

Each permission is assigned a numeric value. Each number from 0 - 7 in binary indicates a unique combination of permissions of rwx.

Calculate the number from 0 to 7 for each access category: user, group, other. Put them together to get a three digit permission number.

To get more information on the chmod command, use the man pages.

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Symbolic Link

Symbloic links are used in UNIX much like a shortcut is used in Windows. A directory can create a link to a file in another directory. To the operating system, this looks like the file exists in the current directory, eventhough it actually exists in a different physical location.

To create a symbolic link:

  1. Change to the directory where the link is to be created.
  2. Issue the ln -s command with the path to the actual file that is being linked
    ln -s /path/to/real/someFile.ext

If the link was created, then you will see the name of the linked file in the current directory, but it will be labeled as a link in a directory lising,
lrwxrwxrwx someFile.ext
This means that the file is a link and that it will have the same permissions as the actual file.

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