9

I'm trying to run a java process via Powershell in Windows XP. Here's the command:

java.exe -cp .;./common.jar -Dcontext=atest1 -Dresourcepath=. DW_Install

So, the classpath is . and .\common.jar (I think java takes the wrong slashes, right?) There are two environment variables, one "atest1" the other "." and the class to execute main on is DW_Install (in the default package).

This command works in cmd.exe, but doesn't is PS. What's going on? What is PS doing while parsing this command that CMD doesn't do (or vice versa)?

Aaron

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2
  • 2
    When you say it doesn't work in Powershell, what actually happens? Commented Jan 13, 2011 at 21:26
  • I get the java.exe help output, as though I just typed java or java -help. Commented Jan 18, 2011 at 16:03

5 Answers 5

Reset to default
11

The problem is that PS for some reason parses -Dresourcepath=. differently than cmd. What works is

java -cp '.;.\common.jar' -Dcontext=atest1 "-Dresourcepath=." DW_Install

It doesn't matter which way the slash goes, and it doesn't matter which quotes one uses (' or "). The classpath must be escaped, however, with some kind of quotes. A good test to see what's getting by the PS interpreter is to echo it. The following:

echo java -cp '.;.\common.jar' -Dcontext=atest1 -Dresourcepath=. DW_Install

yields the following output:

java
-cp
.;.\common.jar
-Dcontext=atest1
-Dresourcepath=
.
DW_Install

(Notice the resourcepath and the value of resourcepath are not on the same line.) Whereas the output to

echo java -cp '.;.\common.jar' -Dcontext=atest1 '-Dresourcepath=.' DW_Install

yields the following output:

java
-cp
.;.\common.jar
-Dcontext=etaste1
-Dresourcepath=.
DW_Install

Which is much more to our liking.

Although I wish this upon none of you, I hope that this post helps those of you that must deploy java projects on Windows machines (even though they will not run on any other platform ever).

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Comments

7

Running external command-line programs from PowerShell is sometimes a bit problematic because there PowerShell exposes two different parsing modes that get trumped by the different syntaxes of said external programs.

In any case, running a command in Powershell requires using either the . prefix (dot-"sourcing") or the & operator.

You can workaround this by passing each parameter to the external program as separate variables, like so:

PS> $classpath = ".;./common.jar"
PS> $env = "-Dcontext=atest1 -Dresourcepath=."
PS> $class = "DW_Install"

PS> . java.exe -cp $classpath $env $class
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3 Comments

typing . java.exe -cp .;.\common.jar -Dcontext=atest1 -Dresourcepath=. DW_Install and . java.exe -cp ".;.\common.jar" -Dcontext=atest1 -Dresourcepath="." DW_Install and . java.exe -cp '.;.\common.jar' -Dcontext=atest1 -Dresourcepath='.' DW_Install don't work either. I am getting to the java.exe process, though, because with the first option, I get the java usage output.
(a) Using . is only required if the name of the program would trigger another parsing mode (7za.exe is an example) but even then you should use & and not . since you are not dot-sourcing an external program. (b) The $env variable will not work as intended.
Although your answer is very good, and fixes many of the problems, 1) it's overkill, 2) it's not entirely accurate. For the proof for 1), see my answer below. for 2), (given that I change $env to $en) I need a different PS variable for each -D argument to make everything work right. This does fix the problem that I noted below (incorrect parsing of resourcepath=.), but it's entirely too cumbersome for my tastes...on second thought, not having to type those environment variables each time may be helpful...thanks again for the post, you get my vote.
3

Another example based on https://gaming.stackexchange.com/questions/24543/how-do-i-change-player-name-in-minecraft-multiplayer-in-offline-mode-in-linux

function mineCraftAs {
    Param (
        [parameter(mandatory=$true, HelpMessage="Minecraft character name." ,ValueFromPipeline=$true)]
        [string] $name
    )
    if(!(test-path $env:appdata)) { $(throw "Appdata not found at $env:appdata")}
    $private:minecraftPath=Join-Path $env:appdata .minecraft
    if(!(test-path $minecraftPath)) { $(throw "Minecraft not found at $minecraftpath")}
    $private:minebinPath=join-path $minecraftPath "bin"
    if(!(test-path $minebinPath)) { $(throw "Minecraft bin not found at $minebinPath")}

    $minebinPath | write-debug
    gci $minebinpath | write-debug

    #java -Xms512m -Xmx1024m -cp "%APPDATA%/.minecraft\bin\*" -Djava.library.path="%APPDATA%\.minecraft\bin\natives" net.minecraft.client.Minecraft '"'%1'"'

    echo java -Xms512m -Xmx1024m  -cp ('"'+$minebinPath+'\*"') ('-Djava.library.path="'+$minebinPath+'\natives"') net.minecraft.client.Minecraft ($name)

    $minecraftJob=& 'C:\Program Files (x86)\Java\jre6\bin\java.exe' -Xms512m -Xmx1024m  -cp ('"'+$minebinPath+'\*"') ('-Djava.library.path="'+$minebinPath+'\natives"') net.minecraft.client.Minecraft ($name)
}
minecraftas newbie
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1 Comment

Thanks for the info! This is a useful example and gets my vote.
1

The following should work:

java.exe -cp '.;./common.jar' -Dcontext=atest1 -Dresourcepath=. DW_Install

I guess that PowerShell interprets the ; in the classpath as command delimiter, thereby trying to run java -cp . and ./common.jar -D....

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1 Comment

Nope, doesn't work, good try, though. I have found the answer, look below.
0 
start-process -nnw java "-cp .;./common.jar -Dcontext=atest1 -Dresourcepath=. DW_Install"
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1 Comment

Thanks for the late answer! I don't have Microsoft Windows anymore nor the project I was trying to run, so I won't be able to verify its validity.

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