Unable to start Selenium server using WebdriverIO on Windows - selenium

Question

I'm following instructions from http://webdriver.io/guide.html
The fourth step mentions this:
java -jar -Dwebdriver.gecko.driver=./geckodriver selenium-server-standalone-3.5.3.jar
After downloading and installing Selenium and WebdriverIO for Windows, I provided the environmental path for all the drivers and executables in System Properties.
I seem to be hitting this issue after I try to execute the aforementioned command through Powershell.
PS C:\webdriverio-test> java -jar -Dwebdriver.gecko.driver=".\geckodriver.exe" .\selenium-server-standalone-3.12.0.jar
Error: Unable to access jarfile .gecko.driver=.\geckodriver.exe
PS C:\webdriverio-test> java -jar -Dwebdriver.gecko.driver=geckodriver.exe .\selenium-server-standalone-3.12.0.jar
Error: Unable to access jarfile .gecko.driver=geckodriver.exe
PS C:\webdriverio-test> java -jar -Dwebdriver.gecko.driver=geckodriver .\selenium-server-standalone-3.12.0.jar
Error: Unable to access jarfile .gecko.driver=geckodriver
PS C:\webdriverio-test> java -jar -Dwebdriver.gecko.driver=./geckodriver .\selenium-server-standalone-3.12.0.jar
Error: Unable to access jarfile .gecko.driver=./geckodriver
If I try running standalone Selenium server without using geckodriver, it works well. However, the main intention is to make it work using geckodriver and something seems to be going wrong here.
It just worked once when I installed it yesterday, but it doesn't seem to be working now. Any pointers as to how to make this work, would be appreciable.
Contents of the directory:
PS C:\webdriverio-test> ls
Directory: C:\webdriverio-test
Mode LastWriteTime Length Name
---- ------------- ------ ----
d----- 5/31/2018 2:41 PM node_modules
d----- 5/31/2018 10:54 AM nssm-2.24
d----- 5/31/2018 10:40 AM test
-a---- 4/8/2018 12:49 PM 9684296 geckodriver.exe
-a---- 5/31/2018 2:41 PM 50430 package-lock.json
-a---- 5/30/2018 3:37 PM 23556263 selenium-server-standalone-3.12.0.jar
-a---- 5/30/2018 4:16 PM 383 test.js
-a---- 5/31/2018 9:31 AM 471 test_2.js
-a---- 5/31/2018 10:51 AM 9875 wdio.conf.js
Thanks in advance.

Answer 1

The jar file must follow the -jar, noting allowed to insert between -jar and the jar file
Execute in Windows CMD：
java -Dwebdriver.gecko.driver=./geckodriver.exe -jar ./selenium-server-standalone-3.12.0.jar
Execute in Windows PowerShell:
java "-Dwebdriver.chrome.driver=chromedriver_2.38.exe" -jar .\selenium-server-standalone-3.12.0.jar
For PowerShell, if the name of -Dname=value includes ., you must use double quote to around the -Dname=value
Note: please use JDK 8 or above.