Python Starting Java application with subprocess:Invalid maximum heap size

Question

I am trying to start a Java application with Python using the subprocess module. I am not new to Python but I am new to the subprocess module. When I try to run this code:

import subprocess as sp
proc = sp.Popen(["java", "-Xmx1536M -Xms1536M", "-jar /home/bekk/MServer/ForgeBukkit/MCPC.jar"],stdin=sp.PIPE,stdout=sp.PIPE,)

The command:

java -Xmx1536M -Xms1536M -jar /home/bekk/MServer/ForgeBukkit/MCPC.jar

runs correctly when typed into a terminal, so I know that it can work. It seems to be a problem with running it from Python. Any thoughts on what my problem might be?

Answer 1

You're passing "-Xmx1536M -Xms1536M" as a single argument.

That's not equivalent to this shell command:

java -Xmx1536M -Xms1536M -jar /home/bekk/MServer/ForgeBukkit/MCPC.jar

… but to this one:

java '-Xmx1536M -Xms1536M' -jar /home/bekk/MServer/ForgeBukkit/MCPC.jar

So, Java will get that '-Xmx1536M -Xms1536M' as its argv[1] , instead of getting one flag in argv[1] and the next in argv[2] . And it will interpret that one giant flag arg as you trying to set mx to '1536M -Xms1536M' , which is not a valid maximum heap size.

To fix it, put each argument in its own string in the list:

["java", "-Xmx1536M", "-Xms1536M", "-jar", "/home/bekk/MServer/ForgeBukkit/MCPC.jar"]