jaas/src/main/java/com/yubico/jaas/impl/YubikeyToUserMapImpl.java
private void add_yubikey_to_user(String publicId, String username, String filename) {
		try {
			File file = new File(filename);
			FileWriter writer = new FileWriter(file, true);
			writer.write("yk." + publicId + ".user = " + username
					+ System.getProperty("line.separator"));
			writer.close();
		} catch (IOException ex) {
			log.error("Failed appending entry to file {}", filename, ex);
		}
	}
private void add_yubikey_to_user(String publicId, String username, String filename) {
		try {
			File file = new File(filename);
			FileWriter writer = new FileWriter(file, true);
			writer.write("yk." + publicId + ".user = " + username
					+ System.getProperty("line.separator"));
			writer.close();
		} catch (IOException ex) {
			log.error("Failed appending entry to file {}", filename, ex);
		}
	}
Stores an association between username and YubiKey publicId in filename.

@param publicId YubiKey public ID to associate with user
@param username username to associate with a YubiKey public ID
@param filename name of the file to store to