Windows has a command-line utility called xcopy, which it inherited from the good old DOS. This utility is very useful when you need to copy a large number of files, especially if they are organized into an elaborate directory tree. Out of the box, you can make xcopy copy only files that already exist in the destination location (just use the /U option); strangely, there is no obvious way to do the opposite — to only copy files that do not exist in the destination location. DOStips.com to the rescue:
for /f %%a in ('xcopy "%source%" "%destination%" /L /Y') do (
if not exist "%destination%.\%%~nxa" xcopy "%%a" "%destination%" /Y
From Institutional Investor:
Inside the Machine: A Journey into the World of High-Frequency Trading
10 Jun 2010
An editor’s journey into the world of high-speed trading and proprietary algorithms that make or break markets.
At 2:45p.m. on Thursday, May 6, George (Gus) Sauter received a frantic call from one of his traders to get in front of a Bloomberg terminal. The Dow Jones industrial average, already down 3.9 percent that day on fears about Greece, was in free fall. In just five minutes the index plunged 573 points. Less than two minutes later, the Dow had rocketed back up 543 points, going on to finish the day down 3.2 percent.
“It was just crazy,” Sauter, chief investment officer of mutual fund giant Vanguard Group, told me a few days later. “I had to go to our fixed-income building, about a five-minute walk from my office. By the time I got there, the market had rallied.”
Crazy, indeed. The aptly named “flash crash” temporarily wiped out more than a half trillion dollars in equity value, shaking what little faith nervous investors had in U.S. markets. Shares of Dow component Procter & Gamble Co., the ultimate defensive blue-chip stock, dropped more than one third in a matter of minutes before recovering almost as quickly, all for no apparent reason. A few other large U.S. companies, including accounting firm Accenture, saw their stocks trade as low as a penny a share, only to close not far from where they had begun the day (nearly $42 a share in the case of Accenture) — again, on no news. By the time the dust settled, a whopping 19.3 billion shares had changed hands, more than twice the average daily U.S. equity market volume this year and the second-biggest trading day ever.