javah

javah(1)                                                              javah(1)



NAME
       javah - C Header and Stub File Generator

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


DESCRIPTION
       javah  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 corre‐
       spond 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 delim‐
       iters.

       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. javah can still  be  used  to
       generate native method function proptotypes needed for JNI-style native
       methods. javah produces JNI-style output by  default,  and  places  the
       result in the .h file.

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

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

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

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

       -verbose
          Indicates verbose output and causes javah to print a message to std‐
          out concerning the status of the generated files.

       -help
          Print help message for javah usage.

       -version
          Print out javah version information.

       -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.

       -classpath path
          Specifies the path javah uses to  look  up  classes.  Overrides  the
          default or the CLASSPATH environment variable if it is set. Directo‐
          ries are separated by colons. Thus the general format for path is:
             .:
          For example:
             .:/home/avh/classes:/usr/local/java/classes

       As a special convenience, a class path element containing a basename of
       * is considered equivalent to specifying a list of all the files in the
       directory with the extension .jar or .JAR (a java program  cannot  tell
       the difference between the two invocations).
       For  example, if directory foo contains a.jar and b.JAR, then the class
       path element foo/* is expanded to a A.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  consist‐
       ing  simply  of * expands to a list of all the jar files in the current
       directory. The CLASSPATH 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  unex‐
       panded  wildcards  except  by querying the environment. For example; by
       invoking System.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 plat‐
          form located in jre/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 option to the Java virtual machine, where option is one of  the
          options  described  on  the  reference page for the java application
          launcher. For example, -J-Xms48m  sets  the  startup  memory  to  48
          megabytes.

ENVIRONMENT VARIABLES
       CLASSPATH
          Used  to provide the system a path to user-defined classes. Directo‐
          ries are separated by colons, for example,


SEE ALSO
       javac, java, jdb, javap, javadoc

                                  05 Aug 2006                         javah(1)