[Preliminaries: the discussion below will refer to a Java class named HelloWorld. Its totally irrelevant to this posting what that class does, since the problem that I describe has to do with the shell, not Java. Its just that the problem arose for me while doing some coding, and I could not think of a more universal illustration.

Nevertheless, if you need something concrete in order to duplicate my actions, then the source file HelloWorld.java that I used contained the text

Code:

public class HelloWorld {
	public static void main(String[] args) {
		System.out.println("Welcome, master");
	}
}

and I compiled using

javac HelloWorld.java

]



Suppose that I execute the following command directly from the shell:

java -XX:OnError="gdb - %p" HelloWorld

Then it works perfectly fine, as expected.

Now suppose that I create the following shell script:

Code:

#!/bin/sh
echo java  -XX:OnError=\"gdb - %p\"  HelloWorld
java  -XX:OnError=\"gdb - %p\"  HelloWorld

The output now is:

java -XX:OnError="gdb - %p" HelloWorld
Unrecognized option: -
Could not create the Java virtual machine.

OK, the echo line outputs exactly what was previously executed directly from the shell, but the script's attempt to execute it fails. The error message hints that the

"gdb - %p"

is actually being interpreted as 3 different words for some strange reason, namely

"gdb
-
%p"

In fact, I think that I can confirm this by modifying the script to be

Code:

#!/bin/sh
echo java  -XX:OnError=\"gdb - %p\"  HelloWorld
set -x
java  -XX:OnError=\"gdb - %p\"  HelloWorld
set +x

which outputs

java -XX:OnError="gdb - %p" HelloWorld
+ java '-XX:OnError="gdb' - '%p"' HelloWorld
Unrecognized option: -
Could not create the Java virtual machine.
+ set +x

Notice how set -x puts the first pair of single quotes around just

-XX:OnError="gdb

and then the next pair around

%p"

So what is the shell script doing in its interpretation of the text that the shell command line does not do that is causing this to fail?

I guess that shell scripts are not exactly like saved command line sessions after all?

Could I work around this by using some sort of octal escape or something for the spaces inside "gdb - %p"?