## Name

javah - C Header and Stub File Generator

f3javah produces C header files and C source files from a Java class. These files provide the connective glue that allow your Java and C code to interact.

## SYNOPSIS

    f3
    javah [ f3optionsf3 ] fully-qualified-classname. . .

## DESCRIPTION

f3javah generates C header and source files that are needed to implement native methods. The generated header and source files are used by C programs to reference an object's instance variables from native source code. The .h file contains a struct definition whose layout parallels the layout of the corresponding class. The fields in the struct correspond to instance variables in the class.

The name of the header file and the structure declared within it are derived from the name of the class. If the class passed to f3javah is inside a package, the package name is prepended to both the header file name and the structure name. Underscores (_) are used as name delimiters.

By default f3javah creates a header file for each class listed on the command line and puts the files in the current directory. Use the f2-stubs option to create source files. Use the f2-o option to concatenate the results for all listed classes into a single file.

The new native method interface, Java Native Interface (JNI), does not require header information or stub files. f3javah can still be used to generate native method function proptotypes needed for JNI-style native methods. f3javah produces JNI-style output by default, and places the result in the .h file.

## OPTIONS

-o outputfile Concatenates the resulting header or source files for all the classes listed on the command line into f2outputfile. Only one of f3-o or f3-d may be used.

-d directory Sets the directory where f3javah saves the header files or the stub files. Only one of f3-d or f3-o may be used.

-stubs Causes f3javah to generate C declarations from the Java object file.

-verbose Indicates verbose output and causes f3javah to print a message to stdout concerning the status of the generated files.

-help Print help message for f3javah usage.

-version Print out f3javah version information.

-jni Causes f3javah to create an output file containing JNI-style native method function prototypes. This is the default output, so use of f3-jni is optional.

-classpath path Specifies the path f3javah uses to look up classes. Overrides the default or the CLASSPATH environment variable if it is set. Directories are separated by colons. Thus the general format for f2path is:

    f3
       .:<your_path>

For example:

    f3
       .:/home/avh/classes:/usr/local/java/classes

As a special convenience, a class path element containing a basename of f2* is considered equivalent to specifying a list of all the files in the directory with the extension f2.jar or f2.JAR (a java program cannot tell the difference between the two invocations).
For example, if directory f2foo contains f2a.jar and f2b.JAR, then the class path element f2foo/* is expanded to a f2A.jar:b.JAR, except that the order of jar files is unspecified. All jar files in the specified directory, even hidden ones, are included in the list. A classpath entry consisting simply of f2* expands to a list of all the jar files in the current directory. The f2CLASSPATH environment variable, where defined, will be similarly expanded. Any classpath wildcard expansion occurs before the Java virtual machine is started -- no Java program will ever see unexpanded wildcards except by querying the environment. For example; by invoking f2System.getenv("CLASSPATH").

-bootclasspath path Specifies path from which to load bootstrap classes. By default, the bootstrap classes are the classes implementing the core Java 2 platform located in f2jre/lib/rt.jar and several other jar files.

-old Specifies that old JDK1.0-style header files should be generated.

-force Specifies that output files should always be written.

-Joption Pass f2option to the Java virtual machine, where f2option is one of the options described on the reference page for the java(1). For example, f3-J-Xms48m sets the startup memory to 48 megabytes.

## ENVIRONMENT VARIABLES

CLASSPATH Used to provide the system a path to user-defined classes. Directories are separated by colons, for example,

    f3

## SEE ALSO

javac(1), java(1), jdb(1), javap(1), javadoc(1)