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. . .
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.
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
stdout 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.
Directories are separated by colons. Thus the general format for
path is:
.:<your_path>
For example:
.:/home/avh/classes:/usr/local/java/classes
As a special convenience, a class path element containing a base‐
name 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 invoca‐
tions).
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 consisting 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 class‐
path 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 Sys‐
tem.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 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(1). 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. Direc‐
tories are separated by colons, for example,
SEE ALSOjavac(1), java(1), jdb(1), javap(1), javadoc(1)
16 Mar 2012 javah(1)