javah - Unix, Linux Command

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NAME

javah - C header and stub file generator

SYNOPSIS

javah [ options ] fully-qualified-classname ...
javah_g [ options ] fully-qualified-classname ...

DESCRIPTION

The javah command 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 instance variables of an object from native source code. The .h file contains a structure definition whose layout parallels that of the corresponding class. The fields in the structure 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 javah 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, javah creates a header file for each class listed on the command line and puts the files in the current directory. Use the -stubs option to create source files. Use the -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. The javah command can still be used to generate native method function prototypes needed for JNI-style native methods. javah produces JNI-style output by default, and places the result in the .h file.

The javah_g version is a non-optimized version of javah suitable for use with debuggers like jdb.

OPTIONS

The following options are supported:

Tag	Description
-o outputfile	Concatenates the resulting header or source files for all the classes listed on the command line into outputfile. Only the -o or -d option may be used.
-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 jre/lib/rt.jar and several other jar files.
-classpath path	Specifies the path javah uses to look up classes. Overrides the default of the CLASSPATH environment variable if it is set. Directories are separated by colons. Thus the general format for path is: Tag Description   .:<your_path> For example:

Tag	Description
	.:/home/avh/classes:/usr/local/java/classes

Tag	Description
-d directory	Sets the directory where javah saves the header files or the stub files.
-force	Specifies that output files should always be written.
-help	Prints help message for javah usage.
-jni	Causes javah to create an output file containing JNI-style native method function prototypes. This is the default output, so use of -jni is optional.
-old	Specifies the old JDK1.0-style header files should be generated.
-stubs	Causes javah to generate C declarations from the Java object file.
-trace	Tracing is no longer supported. Instead, use the -verbose:jni option of the virtual machine.
-verbose	Indicates verbose output and causes javah to print a message to stdout concerning the status of the generated files.
-version	Print out javah version information.
-J option	Pass option to the Java virtual machine, where option is one of the options described on the man page for the java application launcher, java(1). For example, -J-Xms48m sets the startup memory to 48 megabytes. It is a common convention for -J to pass options to the underlying virtual machine.

ENVIRONMENT VARIABLES

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

Tag	Description
	.:/home/avh/classes:/usr/local/java/classes

SEE ALSO

• java (1)

• javac (1)

• javadoc (1)

• javap (1)

• jdb (1)

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