For linux What is the function of "whoami" command? What is the function of "ls" command? What is the name of the default desktop environment of Ubuntu 12.04? Write the necessary commands to display...

Extracted text: For linux What is the function of "whoami" command? What is the function of "ls" command? What is the name of the default desktop environment of Ubuntu 12.04? Write the necessary commands to display the list of the files ending with txt under the current working directory.