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IT Geek: How to Keep Files with the Same Name in Sync

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You have most likely heard of services, such as Dropbox, which are used to keep files in sync across multiple machines. However, what if you want to perform this operation on a single machine? That is, keep files which have the same file name in sync across the machine such that when one of the files changes, they are all updated.

This functionality can be quite useful, especially for developers or system administrators where duplication of files is sometimes required.

How it Works

Suppose you are a web developer who, over the course of time, has put together a nice collection of Javascript functions which you use throughout all the sites you maintain. As you add or improve upon this Javascript file (let’s call it “library.js”), only the current copy you are editing is updated. This would mean, for example, if you make a bug fix or improvement you would have to manually go apply it to each of your other sites’ source code folder as well.

Our tool attempts to solve the problem of having to manually go apply the updated file to each source folder. What it does:

  1. Searches for all files with a specified name (library.js) within a specified root folder (%UserProfile%\Documents\Web Sites).
  2. For all files named library.js, it locates the one which was modified most recently and notes its file hash value.
  3. All other files named library.js (which are not the most recent updated copy) then have their file hash value compared against the most recent (determined in the previous step).
  4. If the file hash values are different, then the respective copy of library.js is replaced with the most recently updated copy.

Because we are using hash values to compare the files, we are assured that any files replaced are indeed different than the most recent copy. For instance, if you were to run the process and 5 file replacements were made, running the process again immediately afterwards would not make any replacements since the file hash values are now identical.

Update to Newest Copy Tool

The Update to Newest Copy Tool tool is a modified version of a batch script with the same name (both are available for download using the links at the bottom of the article) which has been converted to an EXE file in order to include the required Nirsoft HashMyFiles utility. The tool must be run from the command line with certain parameters specified. If you were to just run the EXE file by double-clicking, you will get a message indicating this.

To use Update to Newest Copy, you can view the parameters by running “UpdateToNewestCopy /?” which shows the following dialog:

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The only required parameters are the SourceFolder (e.g. %UserProfile%\Documents\Web Sites) and the FileName (library.js). However, you can alter the functionality by adding additional switches as described above.

Examples

The following command would find all files named “Common.vb” within the folder “C:\users\jfaulkner\documents\Code Files”, performing the replacement but making a backup of the current copy before overwriting (this output is what produced the top image for this article):

UpdateToNewestCopy “C:\users\jfaulkner\documents\Code Files” Common.vb /B

The following command performs the same search action as above, however it only reports on files which would be replaced and does not actually perform any file operations:

UpdateToNewestCopy “C:\users\jfaulkner\documents\Code Files” Common.vb /V

Assume there is a file named “C:\Config\FilesToSearch.txt” with the following contents:

library.js
Common.vb

The following command would search the my documents folder of the current user and report on any updates to “library.js” and “Common.vb”, but would not actually perform any update operations:

UpdateToNewestCopy “%UserProfile%\Documents” “C:\Config\FilesToSearch.txt” /L /V

Automating the Process

This process is an ideal candidate for automation. By creating a scheduled task (nothing special required) with the specified settings and having it run daily/hourly/every 15 minutes (depending on your requirements), you can keep files sync’ed in true set-it-and-forget-it fashion.

Download

Update to Newest Copy – modified executable format

Update to Newest Copy – source batch files (more command line oriented)

Jason Faulkner is a developer and IT professional who never has a hot cup of coffee far away. Interact with him on Google+

  • Published 05/28/13

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