Difference when executing Java command via CMD vs Powershell - caused by periods (".")

Jakg :

I've got an example Java application that requires an HTTP Proxy to be specified in some environments.

When I try running this using the argument as suggested on the Oracle website in CMD (Command Prompt) it works fine.

E:\>java -Dhttp.proxyHost=http://proxy.example.com -jar myJAR.jar
System properties...
[...]
http.proxyHost=http://proxy.example.com

You can see that the application has been run, and when listing the system properties it's correctly received the http.proxyHost property.

However, when I run this from Powershell, I get the following:

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PS E:\> java -Dhttp.proxyHost=http://proxy.example.com -jar myJAR.jar
Error: Could not find or load main class .proxyHost=http:..proxy.example.com

Here it appears some kind of breaking has occurred around the first "." and from then on it's treated the rest as another argument.

If the argument is quoted - e.g. -D"http.proxyHost"=http://proxy.example.com - then it works fine in Powershell.

Can anyone explain this behavior, please?

mklement0 :

Unfortunately, you're seeing a bug in PowerShell, still present as of v7.0:

Something that looks like a parameter to PowerShell is broken into two arguments at the . (period) - even though the argument should simply be passed through, given that an external program is called - see this GitHub issue; in your case, -Dhttp.proxyHost=http://proxy.example.com is unexpectedly passed as -Dhttp .proxyHost=http://proxy.example.com (note the space before the .)

There are two workarounds:

• Quote the . character, using '.':

  java -Dhttp'.'proxyHost=http://proxy.example.com -jar myJAR.jar
  

• Alternatively, as shown in Sergey Shu's answer, use --%, the stop-parsing symbol, to force PowerShell to pass all arguments through without applying PowerShell's usual parsing rules.

  • Caveat: Use of --% has major side effects, notably the inability to use variable references in the command and the inability to apply redirections - see this answer for details.