What is going wrong when Visual Studio tells me “xcopy exited with code 4”

Question

I\'m not very familiar with post-build events, so I\'m a little confused as to what\'s going wrong with my program. When compiling in visual studio 2010, I get the following

Answer 1

I had a post build command that worked just fine before I did an update on VS 2017. It turned out that the SDK tools updated and were under a new path so it couldn't find the tool I was using to sign my assemblies.

This changed from this....

call "%VS140COMNTOOLS%vsvars32"
    "C:\Program Files (x86)\Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.6 Tools\x64\sn.exe" -Ra "$(TargetPath)" "$(ProjectDir)Key.snk"

To This...

"C:\Program Files (x86)\Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.6.1 Tools\x64\sn.exe" -Ra "$(TargetPath)" "$(ProjectDir)Key.snk"

Very subtle but breaking change, so check your paths after an update if you see this error.

Answer 2

I received the 'exited with code 4' error when the xcopy command tried to overwrite a readonly file. I managed to solve this problem by adding /R to the xcopy command. The /R indicates read only files should be overwritten

old command:

XCOPY /E /Y "$(ProjectDir)source file" "destination"

new command

XCOPY /E /Y /R "$(ProjectDir)source file" "destination"

Answer 3

I ran across this issue, so I ran the xcopy command from the command line and it said:

File creation error - The requested operation cannot be performed on a file with
 a user-mapped section open.

It was actually Visual Studio holding onto something. I just restarted Visual Studio and it worked.

Answer 4

I got this along with the message

Invalid drive specification

when copying to a network share without specifying the drive name, e.g.

xcopy . \\localhost

where

xcopy . \\localhost\share

was expected

Answer 5

Switch the watch tab to the "ouput" and look for the xcopy command. Sometimes here you find some more message ( the actual xcopy output ) that could help you to solve the issue. If you don't see the output tab, use View-Output menu to show it.

Answer 6

I addition to the accepted answer, the error can also occur when the destination folder is read-only (Common when using TFS)