How do I copy only changed files

[geoffl]

Hi,
I use a batch file to back up a directory on a computer on my network to my computer. There are 800 small files and it takes some time. Is there a way I could copy only files which have changed since last backup?
Regards
Geoffl

[Geek-9pm]

Make use of the archive attribute.
http://www.computerhope.com/jargon/a/archivea.htm
The backup program  can use this to show a faille has been backed up or not.
Whenever a file is altered, MS-DOS will make the file ready for archive.
http://www.computerhope.com/jargon/a/archival.htm

[DaveLembke]

xcopy also works well for copying only files changed since last backup by looking at date time stamps such as shown below

XCOPY source [destination] [/A | /M] [/D[:date]] [/P] [/S [/E]] [/V] [/W]
                           [/C] [/I] [/Q] [/F] [/L] [/G] [/H] [/R] [/T] [/U]
                           [/K] [/N] [/O] [/X] [/Y] [/-Y] [/Z] [/B]
                           [/EXCLUDE:file1[+file2][+file3]...]

  source       Specifies the file(s) to copy.
  destination  Specifies the location and/or name of new files.
  /A           Copies only files with the archive attribute set,
               doesn't change the attribute.
  /M           Copies only files with the archive attribute set,
               turns off the archive attribute.
  /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.
  /EXCLUDE:file1[+file2][+file3]...
               Specifies a list of files containing strings.  Each string
               should be in a separate line in the files.  When any of the
               strings match any part of the absolute path of the file to be
               copied, that file will be excluded from being copied.  For
               example, specifying a string like \obj\ or .obj will exclude
               all files underneath the directory obj or all files with the
               .obj extension respectively.
  /P           Prompts you before creating each destination file.
  /S           Copies directories and subdirectories except empty ones.
  /E           Copies directories and subdirectories, including empty ones.
               Same as /S /E. May be used to modify /T.
  /V           Verifies the size of each new file.
  /W           Prompts you to press a key before copying.
  /C           Continues copying even if errors occur.
  /I           If destination does not exist and copying more than one file,
               assumes that destination must be a directory.
  /Q           Does not display file names while copying.
  /F           Displays full source and destination file names while copying.
  /L           Displays files that would be copied.
  /G           Allows the copying of encrypted files to destination that does
               not support encryption.
  /H           Copies hidden and system files also.
  /R           Overwrites read-only files.
  /T           Creates directory structure, but does not copy files. Does not
               include empty directories or subdirectories. /T /E includes
               empty directories and subdirectories.
  /U           Copies only files that already exist in destination.
  /K           Copies attributes. Normal Xcopy will reset read-only attributes.
  /N           Copies using the generated short names.
  /O           Copies file ownership and ACL information.
  /X           Copies file audit settings (implies /O).
  /Y           Suppresses prompting to confirm you want to overwrite an
               existing destination file.
  /-Y          Causes prompting to confirm you want to overwrite an
               existing destination file.
  /Z           Copies networked files in restartable mode.
  /B           Copies the Symbolic Link itself versus the target of the link.
  /J           Copies using unbuffered I/O. Recommended for very large files.

The switch /Y may be preset in the COPYCMD environment variable.
This may be overridden with /-Y on the command line.

[Squashman]

When files are changed, it sets the Archive attribute.  So you can use xcopy with the /M option.

[DaveLembke]

When files are changed, it sets the Archive attribute.

Very cool... all these years I didnt know that, and used the date/time stamp instead since it changes when the file is edited and newly created files carry over to the most recent backup. I had always thought that files had to have an attrib function done to them to get the archive attribute tag and then use the /M then to only copy those files, so for years I have been using /D instead of /M. Thanks squashman 

[foxidrive]

robocopy is the upgraded xcopy in Windows these days.

It has a /mir option that creates an exact copy of the folder tree.
  - only copying changed or added files, plus removing files from the target which no longer exist in the source folder.


It's an incredibly powerful copying tool, but don't get the folders wrong.

There's no problem if you use a foldername that does not exist as the target folder, but if you use a different existing folder by mistake then it will be emptied rapidly as robocopy mirrors the source folder.

There are the usual forms of copying too - it is the /MIR switch and /PURGE switch that can bite someone who isn't paying attention.

[geoffl]

Thank you so much. You have saved me 5 minutes every day.
Regards
Geoffl

[DaveLembke]

Cool it all adds up... by the way curious which method you used?

[geoffl]

Just a batch file ' copy t:\dir\*.*  c:\back\dir\*.*'
I just got to work and changed the copy to xcopy and now I get
Invalid drive in search path
Invalid drive in search path
Bad command or file
I am running this under NTVDM Does that make a diffrernce?

[Squashman]

Just a batch file ' copy t:\dir\*.*  c:\back\dir\*.*'
I just got to work and changed the copy to xcopy and now I get
Invalid drive in search path
Invalid drive in search path
Bad command or file
I am running this under NTVDM Does that make a diffrernce?

Please use CODE tags when posting code.  Why are you not using the  /M switch.  That was the whole point of using XCOPY.

Now here is one more point.  Obviously you are obfuscating your code and directory names.  Doing that will a lot of times, not help us figure out what the problem is.  If you are going to obfuscate then you need to still stick to what pattern of what you are actually trying to do.

[geoffl]

 I was using "  copy t:\fms\*.*  c:\back\fms\*.*   "
I changed it to   "  xcopy t:\fms\*.*  c:\back\fms\*.*  /m /y  " and it works fine under the command prompt. It does not work under NTVDM

[foxidrive]

I changed it to   "  xcopy t:\fms\*.*  c:\back\fms\*.*  /m /y  " and it works fine under the command prompt.
It does not work under NTVDM

What are you referring to when you say "NTVDM"?
What error message do you see on the screen?
Use pause as the last line if the window disappears.

[patio]

I despise made up acronyms...

[geoffl]

NT virtual dos machine. Error is bad command or file.

[foxidrive]

NT virtual dos machine. Error is bad command or file.

That error means you typed the command name wrong, or the command is not on the path.
It's not Windows NT line either - "Bad command or filename" is an MSDOS error message.