Command copy exited with code 4 when building - Visual Studio restart solves it

Question

Every now and then when I build my solution here (with 7 projects in it) I get the dreaded 'Command copy exited with code 4' error, in Visual Studio 2010 Premium ed.

This is because of the post-build event not being able to go through.

Here's what solves the problem, temporarily

• Sometimes: A restart of Visual Studio and I'm able to build the solution
• Sometimes: Both a restart of Visual Studio and my file manager of choice (Q-Dir 4.37) solves it.

Here's what the post-build event looks like:

xcopy "$(SolutionDir)Solution Items\References\*.dll" "$(TargetDir)" /Y

When you get the command copy exited with code [insert value] error, it's normally because of the following:

• read / write permissions
• missing files
• wrong directories

However - obviously at times when I build the solution, there's no problem.

FYI, I uninstalled ReSharper 5.1.1 two weeks ago and Visual Studio's been giving me some errors since then (among them not being able to debug). I re-installed Visual Studio and it's working better since then, but still get this problem. Could it have to do with some ReSharper stuff being somewhere?

Have you had the same problem and solved it? Or do you have any possible solution to it?

Diva

Answer 1

I've invariably found this to be a file locking issue. Code 4 is Cannot Access File. One partial solution I found is to use the /C option for xcopy (which continues on error). Not really a solution but mostly it has stopped my builds from failing.

Another solution which only works on 32 bit is to use the unlocker tool to release the windows handles on the file before the copy.

Edit: I've just realised that it works under 64 bits too.

Histone

I added the /C option to above xcopy command and the build succeded. Thanks! Unlocker is invaluable at times. – Diva

I had this issue because one of the files was read-only. Once I changed that, it worked. – Sian

I can also attest that this problem is solved by removing read only permission to offending files. We have an external bin folder that was causing the issue described. Once I removed the read-only attribute, the error dissappeared when trying to build the solution. – Treasure

This unlocker you're pointing to is detected as a virus by just about everything. (google safe browse stuff, eset, virustotal...). seems to be a discussion about it here cnet.com/forums/discussions/unlocker-contains-malware-558941 – Should

Remember how old this answer is. The virus you're alleging actually seems be ad ware stuff that now seems to be bundled into the in the installer not the unlocker software itself. – Histone

Whether it seems to work or not, this is a terrible solution. If a file is locked, it is usually locked for a reason. Probably some other tool is still writing to it, so if xcopy command succeeds, it may have copied an unfinished or truncated file. The /C option causes the file to not be copied at all. If that is acceptable, why do the post-build step in the first place? The proper solution would be to retry xcopy in case of an error. However, if the file is a build output file, then this should probably also reported to Microsoft as a potential bug. – Exocarp

@FlorianWinter - this answer was written nearly 10 years ago. At that time VS was locking files in ways that it no longer needs to do. For the given technologies it might have been overkilll but it was a solution (mostly because getting a fix from microsoft at that time was pretty hard). For modern tooling this is likely no longer the case. – Histone

@PreetSangha The problem still exists with the Visual Studio 2012 compiler, which is old, but not 10 years old (yet), and unfortunately still in use in a lot of projects for various reasons. Oddly, I also found the problem increasing when updating from an old version of MSBuild to the current (2019) one, so I think it is still relevant. And it doesn't change the fact that /C just ignores errors, which may or may not be acceptable. I think at least people considering this solution should know (and your answer says so, which is good - hence no downvote). – Exocarp

@MartinSEk What is /C and the purpose to use? – Kancler

/C allows the commend to return 0 (no error even if it fails). Like I said (which continues on error) – Histone

Answer 2

While /C may ignore errors, it might not be the real solution as there could be files that MUST be copied in order for the build to be successful.

The most common issue is the missing quotes around the pre-defined command tags (such as $TargetDir). When one creates various branches and paths in code or TFS, there is a very high chance for this to occur.

Sometimes if the file is read only, it will cause issues too. Add the /R option to allow read only files to be copied over. You can find list of available options at:

http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/xcopy.mspx?mfr=true

Another possible issue is that the underlying folder cannot be accessed. If so, trying performing "start xcopy" instead of "xcopy". This will open another command window but with admin priveleges.

Heartwhole

'start' fixed it for me...from other forums this seems to be a permissions issue which 'start' resolves, even though the destination has FullControl for 'Everyone' on my box. Also, you can run 'start /MIN xcopy...' to minimize the window flicker – Earreach

I changed c:\windows\system32\xcopy.exe $(TargetPath) <destination path> to c:\windows\system32\xcopy.exe "$(TargetPath)" <destination path> and have no problems in the last 50+ builds. – Romina

I've used "$(OutDir)$(TargetFileName)", changing it to "$(TargetPath)" solves the issue. As does using 'start'! – Polyphagia

My issue seems to be coming from using en-dash character in one of the parent folder name instead of hyphen. I made a mistake of copy/pasting name of the branch folder from word, which was something like "1234 – ABCD". Renamed it to "1234 - ABCD" and xcopy works fine now. – Terbecki

added start and /R, just in case... not sure which one did the trick, but it worked! Thanks! – Osgood

Thumbs up for start xcopy – Amora

start xcopy worked but I don't understand why my new assembly can't be accessed without it – Totter

Using start most likely "works" because it runs the command asynchronously, so it trivially doesn't fail even if it fails eventually. It just disables error handling and thus has a similar effect as /C. Even if it does actually help, you sill don't have error handling, and you have no guarantee that the copy operation is finished before dependent projects are being built. – Exocarp

Answer 3

I crossed the same error, but it is not due to the file is locked, but the file is missing.

The reason why VS tried to copy an not existing file, is because of the Post-build event command.

After I cleared that, problem solved.

UPDATE:

As @rhughes commented:

The real issue is how to get the command here to work, rather than to remove it.

and he is absolutely right.

Sauceda

If you were copying a file during post-build, chances are the reason is because you have entered a command here. The real issue is how to get the command here to work, rather than to remove it. – Tales

Answer 4

I have also faced this problem.Double check the result in the error window.

In my case, a tailing \ was crashing xcopy (as I was using $(TargetDir)). In my case $(SolutionDir)..\bin. If you're using any other output, this needs to be adjusted.

Also note that start xcopy does not fix it, if the error is gone after compiling. It might have just been suppressed by the command line and no file has actually been copied!

You can btw manually execute your xcopy commands in a command shell. You will get more details when executing them there, pointing you in the right direction.

Kenning

The same happened for me with the $(OutDir). It seems that all the path macros have a "\" at the end and it crashes xcopy – Falsify

Answer 5

In case the post build event contains copy/xcopy command for copying build output to some directory(which usually is the most common post build operation) the problem can occur in case the full directory path either of source or target destinations contain folder names which include spaces. Remove space for the directory name(s) and try.

Emalee

Answer 6

As mentioned in many sites, there are various reasons for this. For me it was due to the length of Source and Destination (Path length). I tried xcopy in the command prompt and I was unable to type the complete source and path (after some characters it wont allow you to type). I then reduced the path length and was able to run. Hope this helps.

Blunger

Answer 7

This can happen in multiple cases:

1. When the complete string path is longer than 254 chars.
2. When the name of the file to be copied is wrong.
3. When the target path is wrong.
4. When the readonly attribute is set on the copied file or target folder.

Aldred

Answer 8

I got this error because the user account that TFS Build Service was running under did not have permissions to write to the destination folder. Right-click on the folder-->Properties-->Security.

Naturalize

Hats off to "Tangodancer" and or "Abdul Rahman". Right-click on the folder-->Properties-->Security solved the problem for me on a stand alone XP SP3 system Thank YOU – Sining

Answer 9

Run VS in Administrator mode and it should work fine.

Corniculate

I am running VS as Administrator but this did not work for me. – Scouting

Some users may be unable to run in Administrator mode. – Dumfries

Answer 10

I got this error because of the file was opened in another instance.

when i closed the file and again re-build the solution, it was successfully copied.

Reprovable

Answer 11

I faced the same issue in case of XCOPY after build is done. In my case the issue was happening because of READ-ONLY permissions set on folders.

I added attrib -R command before XCOPY and it solved the issue.

Hope it helps someone!

Reinertson

Answer 12

I had the same error with xcopy in connection with the Test Engine. I am using VisualStudio Professional 2013. By default Test -> Test Settings -> Keep Test Execution Engine Running seems to be the reason for my error code 4 with xcopy. Switching it off solved the problem. The execution engine seems to keep hold on some .dlls.

Hieratic

Answer 13

I had the same problem. A simple 'Clean Solution' in VS cleared the error, but it was a temporary solution.

Fulminant

I am getting this problem and "Clean Solution" did not help me. Does "Clean Solution" work for you every time? – Miter

Answer 14

I found that setting the file's Copy To Output Directory parameter to Copy Always seems to have cleared up the locking issue. Although now I have 2 copies of the files and need to delete one.

Battle

Answer 15

I had the same problem. However, nothing worked for me. I solved the issue by adding

exit 0

to my code. The problem was that while I was doing copying of the files, sometimes the last file could not be found, and the bat returned a non-zero value.

Hope this helps someone!

Preconceive

Answer 16

If you are running Windows 7 onward, you can try the new 'robocopy' command:

robocopy "$(SolutionDir)Solution Items\References\*.dll" "$(TargetDir)"

More information about robocopy can be found here.

Tales

Answer 17

I faced same issue. I deleted post-build events and it started working. Some times when we add some SQL components it may add post build commands also.

Gnathic

Answer 18

I am getting something similar using an xcopy with the /exclude option. In my case, I found that editing the post-build event (something harmless like a newline after the command) and saving the project causes the error to happen. Re-saving the file specified in the /exclude option causes it to work again.

Minervamines

Answer 19

As I am writing a DLL library I used the xcopy command to copy the library where the program can find and load it. After several times of opening and closing the program there was still an open process of it in taskmanager which i did not recognized.

Look for any process from which the file may be used and close it.

Tumular

Answer 20

What fixed it for me: dig down to the specific solution for the project you want i.e NOT the overall solution file for all the projects.

Do try - I tried everything else mentioned here but to no avail.

Seurat

Answer 21

I don't see anything in here to suggest that this is a web-app but I have experienced this issue myself - I've got two xcopy commands on a post-build event and only one of them was failing. Something had a lock on the file, and it wasn't Visual Studio (as I tried restarting it.)

The only other thing that would have used the dll I built was IIS. And lo and behold,

A simple iisreset did the trick for me.

Deutzia

Answer 22

I had the same issue. It was caused by having the same flag twice, for example:

if $(ConfigurationName) == Release (xcopy "$(TargetDir)." "$(SolutionDir)Deployment\$(ProjectName)\" /e /d /i /y /e)

Observe that the "/e" flag appears twice. Removing the duplicate solved the issue.

Sportsman

Answer 23

In my case my $(OutDir) was simply ..\..\Build\ i.e. some relative path. And, when I was trying to xcopy as follows xcopy /y "$(OutDir)Proj1.dll" "Anypath\anyfolder\" I was getting the exit code error 4.

What's happening was, this command was getting executed in the $(OutDir) (in my case build folder) itself and not the directory where the csproj file of the project was located (as we would normally expect). Hence, I kept getting File not found error (corresponding to exit code 4).

I couldn't figure this out until I wrote cd in the Post Build events, to print which directory this was getting executed in.

So, to summarize, if we're wishing to copy / xcopy files from the $(OutDir), either use "$(TargetDir)" (which is complete path for output directory) or need not specify any path at all.

Scarlatina

Answer 24

Can be caused by VMWare Workstation with Shared Folders

I have the problem always when the destinatinon folder of the xcopy is also mapped as Shared Folder in a VM.

I solved it with a script running in the vm and deleting the content of the shared folder.

Gurgle

Answer 25

To expand on rhughes answer,

The robocopy works beautifully, just incase you need to include sub directories you can use /e to include subs and copy empty directories or /s to include subs excluding empty directories.

Also robocopy will report back a few things like if new files were copied, this will cause VS to complain since anything above 0 is a failure and robocopy will return 1 if new files have been found. Its worth to mention that robocopy first compares the Source/Dest and only copies the updated/new files.

To get around this use:

(robocopy "$(SolutionDir)Solution Items\References\*.dll" "$(TargetDir)") ^& IF %ERRORLEVEL% LEQ 4 exit /B 0

Octangle

Answer 26

If you are here because your project fails to build on a build server, but builds fine "manually" on a dev machine, and you are doing xcopy only for debugging and to emulate a production environment on a dev machine, then you may want to look at this solution:

https://mcmap.net/q/152814/-can-you-prevent-msbuild-exe-from-running-build-events

You simply turn off post build events on the build server using

msbuild foo.sln /p:PostBuildEvent=

This is not good enough if you have other post build events that also need to run on the build server, and it is not a general solution. However, since there are so many different causes of this problem, there cannot be a general solution. One of the many answers to this question (and its duplicates) will probably help, but be careful with approaches that only somehow circumvent error handling (such as xcopy /C). Those may work for you, particularly also in the build server scenario, but I think this one is more reliable, IF it can be used.

It has also been suggested that with newer versions of Visual Studio, the problem no longer exists, so if you are using an old version, consider updating your build tools.

Exocarp

Answer 27

Error code 4 can mean a lot of things, so I recommend reading the other answers as well until you find a solution that works for you AND you understand WHY it works (some solutions only disable error handling, which may only mask the problem but not solve it).

This can be a file locking issue related to parallel building. A workaround is to not use parallel building. This is the default behavior, but if you are using the -m option, then projects will be built in parallel. The following variations should not build projects in parallel, so you will not run into the file locking problem.

msbuild -m:1
msbuild -maxcpucount:1
msbuild

Note that, contrary to what has been said here, this even happens with the "latest" version of MSBuild (from Build Tools for Visual Studio 2019).

The best solution is probably to make sure you don't need to copy files in a post-build step. In some situations, you can also disable post-build steps when building with MSBuild on a build server: https://mcmap.net/q/151107/-command-copy-exited-with-code-4-when-building-visual-studio-restart-solves-it

Exocarp

Answer 28

I want to amplify and crystallize these two answers: @Vemul's, @Srihari Chinna's.

• Make sure that your source path exists and that the process has access to it.
  • This is especially true if you're using variable substitution to assemble the source path.

Daimon