textbook gives a string of code, configure environment variables before each run in a specific folder, report an error when starting "Cygwin" and return an error, I think it is still the problem of unix format and windows doc format carriage return, you are instructed how to use the "ultraedit" software to save unix format files, the red box below is the menu of "ultraedit", under the instructions, the green box is the "language type view way" that I found in the "encoder bar".