These options test for particular types of files. (Everything’s a file, but not all files are the same!)
True if file exists and is a block special device.
True if file exists and is a character special device.
True if file exists and is a directory.
True if file exists and is a regular file.
True if file exists and is a symbolic link. Unlike all other file-related tests, this test does not dereference file if it is a symbolic link.
True if file exists and is a named pipe.
True if file exists and is a socket.
True if fd is a file descriptor that is associated with a terminal.