Obtain build logs with MSBuild
By using command-line options with MSBuild, you can specify how much build data you want to review and whether you want to save build data to one or more files. You can also specify a custom logger to collect build data. For information about MSBuild command-line options that this topic doesn't cover, see Command-line reference.
Note
If you build projects by using the Visual Studio IDE, you can troubleshoot those builds by reviewing build logs. For more information, see How to: View, save, and configure build log files.
Set the level of detail
When you build a project by using MSBuild without specifying a level of detail, the following information appears in the output log:
Errors, warnings, and messages that are categorized as highly important.
Some status events.
A summary of the build.
By using the -verbosity (-v) switch, you can control how much data appears in the output log. For troubleshooting, use a verbosity level of either detailed (d) or diagnostic (diag), which provides the most information.
The build process may be slower when you set the -verbosity to detailed and even slower when you set the -verbosity to diagnostic.
msbuild MyProject.proj -t:go -v:diag
Verbosity settings
The following table shows how the log verbosity (column values) affects which types of message (row values) are logged.
| Message type / Verbosity | Quiet | Minimal | Normal | Detailed | Diagnostic |
|---|---|---|---|---|---|
| Errors | ✅ | ✅ | ✅ | ✅ | ✅ |
| Warnings | ✅ | ✅ | ✅ | ✅ | ✅ |
| High-importance Messages | ✅ | ✅ | ✅ | ✅ | |
| Normal-importance Messages | ✅ | ✅ | ✅ | ||
| Low-importance Messages | ✅ | ✅ | |||
| Additional MSBuild-engine information | ✅ |
Save the build log to a file
You can use the -fileLogger (fl) switch to save build data to a file. The following example saves build data to a file that's named msbuild.log.
msbuild MyProject.proj -t:go -fileLogger
In the following example, the log file is named MyProjectOutput.log, and the verbosity of the log output is set to diagnostic. You specify those two settings by using the -fileLoggerParameters (flp) switch.
msbuild MyProject.proj -t:go -fl -flp:logfile=MyProjectOutput.log;verbosity=diagnostic
For more information, see Command-line reference.
Save the log output to multiple files
The following example saves the entire log to msbuild1.log, just the errors to JustErrors.log, and just the warnings to JustWarnings.log. The example uses file numbers for each of the three files. The file numbers are specified just after the -fl and -flp switches (for example, -fl1 and -flp1).
The -fileLoggerParameters (flp) switches for files 2 and 3 specify what to name each file and what to include in each file. No name is specified for file 1, so the default name of msbuild1.log is used.
msbuild MyProject.proj -t:go -fl1 -fl2 -fl3 -flp2:logfile=JustErrors.log;errorsonly -flp3:logfile=JustWarnings.log;warningsonly
If you're using a shell that interprets semicolons (for example, bash), put single or double quotes around any option that has semicolons to prevent it from being interpreted as a command separator. For more information, see Command-line reference.
Save a binary log
You can save the log in compressed, binary format using the -binaryLogger (bl) switch. This log includes a detailed description of the build process and can be read by certain log analysis tools.
In the following example, a binary log file is created with the name binarylogfilename.
-bl:binarylogfilename.binlog
You can use the Structured log viewer to view binary logs in a way that makes it much easier to see what is going on.
For more information, see Command-line reference.
Use a custom logger
You can write your own logger by authoring a managed type that implements the ILogger interface. You might use a custom logger, for instance, to send build errors in email, log them to a database, or log them to an XML file. For more information, see Build loggers.
In the MSBuild command line, you specify the custom logger by using the -logger switch. You can also use the -noconsolelogger switch to disable the default console logger.