/Log (devenv.exe)
Applies to: 
Visual Studio 
Visual Studio for Mac
Note
This article applies to Visual Studio 2017. If you're looking for the latest Visual Studio documentation, see Visual Studio documentation. We recommend upgrading to the latest version of Visual Studio. Download it here
Logs all activity to the log file for troubleshooting. This file appears after you've called devenv /log at least once. By default, the log file is located here:
%APPDATA%\Microsoft\VisualStudio\<Version>\ActivityLog.xml
where <Version> is the Visual Studio version. However, you may specify a different path and file name.
Syntax
devenv /Log NameOfLogFile
Arguments
NameOfLogFile
Required. The full path and name of the log file to save to.
Remarks
This switch must appear at the end of the command line, after all other switches.
The log is written only for all instances of Visual Studio that you've opened with the /Log switch.
Example
This example directs logging to the MyVSLog.xml file in the user's home directory.
devenv /log "%USERPROFILE%\MyVSLog.xml"