4 Invoking gij

gij is a Java bytecode interpreter included with libgcj. gij is not available on every platform; porting it requires a small amount of assembly programming which has not been done for all the targets supported by gcj.

The primary argument to gij is the name of a class or, with -jar, a jar file. Options before this argument are interpreted by gij; remaining options are passed to the interpreted program.

If a class name is specified and this class does not have a main method with the appropriate signature (a static void method with a String[] as its sole argument), then gij will print an error and exit.

If a jar file is specified then gij will use information in it to determine which class' main method will be invoked.

gij will invoke the main method with all the remaining command-line options.

Note that gij is not limited to interpreting code. Because libgcj includes a class loader which can dynamically load shared objects, it is possible to give gij the name of a class which has been compiled and put into a shared library on the class path.

-cp path

-classpath path

Set the initial class path. The class path is used for finding class and resource files. If specified, this option overrides the CLASSPATH environment variable. Note that this option is ignored if -jar is used.

-Dname[=value]

This defines a system property named name with value value. If value is not specified then it defaults to the empty string. These system properties are initialized at the program's startup and can be retrieved at runtime using the java.lang.System.getProperty method.

-ms=number

Equivalent to -Xms.

-mx=number

Equivalent to -Xmx.

-noverify

Do not verify compliance of bytecode with the VM specification. In addition, this option disables type verification which is otherwise performed on BC-ABI compiled code.

-X

-Xargument

Supplying -X by itself will cause gij to list all the supported -X options. Currently these options are supported:

-Xmssize

Set the initial heap size.

-Xmxsize

Set the maximum heap size.

-Xsssize

Set the thread stack size.

Unrecognized -X options are ignored, for compatibility with other runtimes.

-jar

This indicates that the name passed to gij should be interpreted as the name of a jar file, not a class.

--help

-?

Print help, then exit.

--showversion

Print version number and continue.

--fullversion

Print detailed version information, then exit.

--version

Print version number, then exit.

-verbose

-verbose:class

Each time a class is initialized, print a short message on standard error.

gij also recognizes and ignores the following options, for compatibility with existing application launch scripts: -client, -server, -hotspot, -jrockit, -agentlib, -agentpath, -debug, -d32, -d64, -javaagent, -noclassgc, -verify, and -verifyremote.