That means that lack of write permission on a directory does not prevent a user from modifying a file within the directory, if the file's permissions allow it. It does prevent the user from renaming, moving, deleting or creating any file in the directory. This is because a directory is a really a file that contains a list of filenames, and so read and write permission control access to that list. Since write permission allows the modification of directory entries, a user can move or rename a file without permission to examine the contents . This is a very good reason for paying attention to write access for important directories.
Execute permission is necessary for accessing a directory.
Permission denied This copy of .bashrc does not do us a lot of good. However, setting execute permission for directory and not setting read or write can come in handy. In the first command, we see that we can set options for more than one class at a time by using a comma to separate the mode specifications. Here, we set the mode so that no user has execute permission. In the second command, we try to set execute permission for other with X .