By default, copying from the command prompt will prompt you to overwrite files that already exist in the target location.
You can add "/Y" to say "Yes to all" replacements.
But how can you say "No to all" ?
In other words, I want to copy everything from one directory that does not already exist in the target.
The closest thing I see is the XCOPY argument to only copy things after a specific mod-datetime.
Unless there's a scenario where you'd not want to copy existing files in the source that have changed since the last copy, why not use XCOPY with /D without specifying a date?
You can make a text file with a single long line of "n" then run your command and put < nc.txt after it. I did this to copy over 145,000 instances where "No overwrite" was what I wanted and it worked fine this way.
Or you can just hold the n key down with something, but that takes longer than using the < to pipe it in.
Here's a workaround. If you want to copy everything from A that does not already exist in B:
Copy A to a new directory C. Copy B to C, overwriting anything that overlaps with A. Copy C to B.
I use XCOPY with the following parameters for copying .NET assemblies:
/D /Y /R /H
/D:m-d-y - Copies files changed on or after the specified date. If no date is given, copies only those files whose source time is newer than the destination time.
/Y - Suppresses prompting to confirm you want to overwrite an existing destination file.
/R - Overwrites read-only files.
/H - Copies hidden and system files also.
I expect xxcopy has an option for that.
Bingo:
http://www.xxcopy.com/xxcopy27.htm#tag_231
2.3 By comparison with the file in destination
The switches in this group select files based on the
comparison between the files in the source and those in
the destination. They are often used for periodic backup
and directory synchronization purposes. These switches
were originally created as variations of directory backup.
They are also convenient for selecting files for deletion.
2.3.1 by Presence/Absence
The /BB and /U switches are the two switches which select
files by the pure presence or absence as the criteria.
Other switches in the this group (Group 2.3) are also
affected by the file in the destination, but for a
particular characteristics for comparison's sake.
/BB Selects files that are present in source but not in destination.
/U Selects files that are present in both source and destination.
-Adam
Depending on the size and number of files being copied, you could copy the destination directory over the source first with "yes to all", then do the original copy you were doing, also with "yes to all" set. That should give you the same results.
Adding the switches for subdirectories and verification work just fine. echo n | xcopy/-Y/s/e/v c:\source*.* c:\Dest\