Thursday, July 11, 2013

Touching a file (changing last updated Date/time) with the COPY command. Here's how and a little history too.

The Old New Thing - Why is the syntax for touching a file from the command prompt so strange?

The magic incantation for updating the last-modified date on a file is


What strange syntax! What's with the plus sign and the commas, anyway?

The formal syntax is the much more straightforward


This means to start with the file A, then append the files B, C, and D, treating them all as binary files.

If you omit the B+C+D part, then you get ...


This means "Start with A, then append nothing." The side effect is that the last-write time gets updated, because the command processor opens A for append, writes nothing, then closes the handle.



As you know, I love these kinds of posts. First off I didn't know you could even do this with the COPY command, secondly I had to laugh that he tried it on MS-DOS versions all the way back to 2.1 and finally the reminder that backward compatibility can be a...

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