Obtain build logs with MSBuild

By using switches 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 switches 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.

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 -filelogparameters (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 -filelogparameters (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

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

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.

See also