What causes "Failed to create the jython-src directory at: {jythonSrcDestDir}" in NationalSecurityAgency/ghidra?

Inspect /dev/jython_cachedir and remove any non-directory entry named jython-src, then retry.

NationalSecurityAgency/ghidra · error · IOException

Failed to create the jython-src directory at: {jythonSrcDest

Error message

Failed to create the jython-src directory at: {jythonSrcDestDir}

What it means

Thrown by JythonUtils.setupJythonCacheDir() when FileUtilities.createDir() fails on the 'jython-src' subdirectory inside the cache (<settings>/dev/jython_cachedir/jython-src). Occurs immediately after the cache dir itself was created successfully, so it points to a problem creating one nested folder (race, permission inheritance, or an existing non-dir entry).

Source

Thrown at Ghidra/Extensions/Jython/src/main/java/ghidra/jython/JythonUtils.java:77

	 * some installations will not have the appropriate directory permissions to create new files in.
	 * 
	 * @param monitor A monitor to use during the cache directory setup.
	 * @return The jython cache directory.
	 * @throws IOException If there was a disk-related problem setting up the cache directory.
	 * @throws CancelledException If the user cancelled the setup.
	 */
	public static File setupJythonCacheDir(TaskMonitor monitor)
			throws CancelledException, IOException {

		File devDir = new File(Application.getUserSettingsDirectory(), "dev");
		File cacheDir = new File(devDir, JYTHON_CACHEDIR);
		if (!FileUtilities.mkdirs(cacheDir)) {
			throw new IOException("Failed to create the jython cache directory at: " + cacheDir);
		}

		File jythonSrcDestDir = new File(cacheDir, JYTHON_SRC);
		if (!FileUtilities.createDir(jythonSrcDestDir)) {
			throw new IOException(
				"Failed to create the " + JYTHON_SRC + " directory at: " + jythonSrcDestDir);
		}

		File jythonModuleDir = Application.getMyModuleRootDirectory().getFile(false);
		File jythonSrcDir = new File(jythonModuleDir, JYTHON_SRC);
		if (!jythonSrcDir.exists()) {
			try {
				jythonSrcDir = Application.getModuleDataSubDirectory(jythonModuleDir.getName(),
					JYTHON_SRC).getFile(false);
			}
			catch (FileNotFoundException e) {
				throw new IOException("Failed to find the module's " + JYTHON_SRC + " directory");
			}
		}

		try {
			FileUtilities.copyDir(jythonSrcDir, jythonSrcDestDir, f -> f.getName().endsWith(".py"),
				monitor);

View on GitHub (pinned to d5f144c24d)

Solutions

Inspect <settings>/dev/jython_cachedir and remove any non-directory entry named jython-src, then retry.
Verify the user can create subdirectories inside jython_cachedir (permissions/SELinux context).
Clear the whole jython_cachedir and let setup rebuild it from scratch.

Example fix

null

Defensive patterns

Strategy: validation

Validate before calling

import java.io.File;
File jsrc = new File(new File(new File(
    Application.getUserSettingsDirectory(), "dev"), "jython_cachedir"), "jython-src");
if (jsrc.exists() && !jsrc.isDirectory()) {
    // a file is blocking the dir creation; remove it before init
}

Type guard

null

Try / catch

try {
    GhidraJythonInterpreter.get();
} catch (NullPointerException npe) {
    // clean jython_cachedir and retry once
}

Prevention

Clear <settings>/dev/jython_cachedir if a previous run left junk.
Avoid concurrent interpreter initializations sharing one cache.
Ensure consistent permissions on nested cache subdirectories.

When it happens

Trigger: Cache directory exists but the jython-src child cannot be created; e.g. an existing file named jython-src, a transient I/O error, or a filesystem that disallowed the nested mkdir.

Common situations: A leftover file (not directory) named 'jython-src' from a prior crashed run inside jython_cachedir; antivirus/SELinux blocking nested dir creation; concurrent interpreter inits racing on the same cache.

Related errors

AI-assisted analysis of NationalSecurityAgency/ghidra@d5f144c24d (2026-08-14). Data as JSON: /api/errors/f6d3c5d53915257b. Report an issue: GitHub.