Dear, engineer! I'm writing this E-mail to you since I think I've found something wrong in Ubuntu! My Operating System here is Ubuntu Kylin 14.04. I find a question about command 'paste' in command line. Support there is a file called "test.txt", and its content is the next 2 lines: ab cd If I run the command "paste test.txt", the content of this file will be print at STDOUT. However, when I ran the command "paste test.txt > test.txt" I found that the file "test.txt" became an empty file. Here comes the question, what's going on? Can you help me? Yours faithfully, Quan Liu from Central South University! 2015-07-24 Quan Liu