To open the Gnome Nautilus file manager from the command line in Linux or Unix, you can use the following command:
nautilus .
The . (dot) at the end of the command specifies the current directory. Nautilus will open with the current directory as the root directory.
Alternatively, you can specify a different directory by replacing the . with the path to the desired directory:
nautilus /path/to/directory
This will open Nautilus with the specified directory as the root directory.