[maven] Maven command to determine which settings.xml file Maven is using

How do I use maven command line to determine which settings.xml file Maven is picking up?

You can use the maven help plugin to tell you the contents of your user and global settings files.

mvn help:effective-settings

will ask maven to spit out the combined global and user settings.

Your comment to cletus' (correct) answer implies that there are multiple Maven settings files involved.

Maven always uses either one or two settings files. The global settings defined in (${M2_HOME}/conf/settings.xml) is always required. The user settings file (defined in ${user.home}/.m2/settings.xml) is optional. Any settings defined in the user settings take precedence over the corresponding global settings.

You can override the location of the global and user settings from the command line, the following example will set the global settings to c:\global\settings.xml and the user settings to c:\user\settings.xml:

mvn install --settings c:\user\settings.xml 
    --global-settings c:\global\settings.xml

Currently there is no property or means to establish what user and global settings files were used from with Maven. To access these values, you would have to modify MavenCli and/or DefaultMavenSettingsBuilder to inject the file locations into the resolved Settings object.

Quick and dirty method to determine if Maven is using desired settings.xml would be invalidate its xml and run some safe maven command that requires settings.xml.

If it reads this settings.xml then Maven reports an error: "Error reading settings.xml..."

The M2_HOME environment variable for the global one. See Settings Reference:

The settings element in the settings.xml file contains elements used to define values which configure Maven execution in various ways, like the pom.xml, but should not be bundled to any specific project, or distributed to an audience. These include values such as the local repository location, alternate remote repository servers, and authentication information. There are two locations where a settings.xml file may live:

• The Maven install: $M2_HOME/conf/settings.xml
• A user's install: ${user.home}/.m2/settings.xml

This is the configuration file for Maven. It can be specified at two levels:

1. User Level. This settings.xml file provides configuration for a single user, and is normally provided in ${user.home}/.m2/settings.xml.

             NOTE: This location can be overridden with the CLI option:
   
             -s /path/to/user/settings.xml
   

2. Global Level. This settings.xml file provides configuration for all Maven users on a machine (assuming they're all using the same Maven installation). It's normally provided in ${maven.home}/conf/settings.xml.

             NOTE: This location can be overridden with the CLI option:
   
             -gs /path/to/global/settings.xml
   

If you are debugging and wasting time like me, this will give exact details including passwords. :P

mvn help:effective-settings -DshowPasswords=true