Gradle: getting the root project directory path when starting with a custom build file

I got past this problem by ensuring Java userDir was set to the project directory (i.e. project.projectDir) at the top of my build.gradle file, as follows:

    System.setProperty( "user.dir", project.projectDir.toString() )
    println  "  project dir:  "+ System.getProperty("user.dir");

This can be checked by executing a separate (Groovy) code file such as:

    println "User Dir: ${System.getProperty( 'user.dir' )}"

You can output the Gradle project values before and after using these statements.

    println  "Root project:   ${project.rootProject}";
    println  "  rootDir:      ${project.rootDir}"
    println  "  projectDir:   ${project.projectDir}";
    println  "  project dir:  ${System.getProperty("user.dir")}";

If you have sub-projects, projectDir is not the same as rootDir.

This hasn’t fixed my actual problem but it has ensured that I’m opening the correct file (relative to the location of build.gradle.