File command in Java

Is there an equivalent package in Java for the 'file' command on Unix? I want to determine the file type from the Data, not the extension or MIME type.
Thx.
--jon

If you're on UNIX, you may 'exec' the 'file' application and capture the app's output using the process's input stream. Then parse the returned info to determine file type.

Similar Messages

Can you execute a class file without invoking the command line java command

I am running java on a Windows XP equipped machine, and I am wondering if it is possible to execute a class file by double clicking the file icon, or can it only be done via command line. So far I have been unsuccessful in my attempts - I tried associating the class file with the java executable in my JRE directory, but that didn't work.
Many thanks,
-Stile

nope, can't be done, by design... microsoft recognised java as threat to the empire very early on in the peace.... but you can write a batch file to execute myprogram.class called myprogram.bat and stick it in your PATH.
keith.

How to Install .CAP file in the Java Card?

Hi Friends..
How to install *.CAP* file in the Java Card?..
I've GPShell script as follows :
mode_211
enable_trace
establish_context
card_connect -readerNumber 2
open_sc -security 1 -keyind 0 -keyver 0 -mac_key 404142434445464748494a4b4c4d4e4f -enc_key 404142434445464748494a4b4c4d4e4f
install_for_load -pkgAID a00000006203010c01 -nvCodeLimit 500 -sdAID A000000003000000
load -file HelloWorld.cap
card_disconnect
release_contextwith that script i can load HelloWorld.cap file successfully..
Now, how to install the HelloWorld.cap file?..
if i add script : load -file HelloWorld.cap i got this error :
install -file HelloWorld.cap
file name HelloWorld.cap
Command --> 80E602001B09A00000006203010C0107A00000015100000006EF04C60201A80000
Wrapped command --> 84E602002309A00000006203010C0107A00000015100000006EF04C60201
A80030C859793049B85300
Response <-- 6985
install_for_load() returns 0x80206985 (6985: Command not allowed - Conditions of
use not satisfied.)i ask this question because when i tried to select the applet through its AID, by this script :
establish_context
card_connect -readerNumber 2
select -AID a00000006203010c0101i got this message error : select_application() returns 0x80216A82 (6A82: The application to be selected could not be found.)
but there's exactly any that AID in my Java Card..
here's is the list of AID from My Java Card :
C:\GPShell-1.4.2>GPShell listgp211.txt
mode_211
enable_trace
establish_context
card_connect -readerNumber 3
* reader name OMNIKEY CardMan 5x21-CL 0
select -AID a000000003000000
Command --> 00A4040008A000000003000000
Wrapped command --> 00A4040008A000000003000000
Response <-- 6F108408A000000003000000A5049F6501FF9000
open_sc -security 1 -keyind 0 -keyver 0 -mac_key 404142434445464748494a4b4c4d4e4
f -enc_key 404142434445464748494a4b4c4d4e4f // Open secure channel
Command --> 80CA006600
Wrapped command --> 80CA006600
Response <-- 664C734A06072A864886FC6B01600C060A2A864886FC6B02020101630906072A864
886FC6B03640B06092A864886FC6B040215650B06092B8510864864020102660C060A2B060104012
A026E01029000
Command --> 8050000008AAF7A87C6013BC0300
Wrapped command --> 8050000008AAF7A87C6013BC0300
Response <-- 0000715457173C2A8FC1FF0200937A55C288805D8F2A04CCD43FA7E69000
Command --> 848201001023CA18742D36165ED992CFF2146C3D51
Wrapped command --> 848201001023CA18742D36165ED992CFF2146C3D51
Response <-- 9000
get_status -element 10
Command --> 80F21000024F0000
Wrapped command --> 84F210000A4F004FF8BE1492F7275400
Response <-- 0CF0544C00004D4F44554C415201000009A00000006203010C010100010AA000000
06203010C01019000
GP211_get_status() returned 2 items
List of Ex. Load File (AID state Ex. Module AIDs)
f0544c00004d4f44554c4152        1
a00000006203010c01      1
        a00000006203010c0101
card_disconnect
release_contextPlease help me..
And please correct me if i'm wrong,,
Thanks in advance..

Any suggestions for my question?..
Please help me..
Thanks in advance..

Executing UNIX command in Java

I am having problems executing a command in Java. Here's the code I have for executing:
Process p = Runtime.getRuntime().exec(cmd);
                                        BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream()));
     while((display = input.readLine()) != null)
                         num_1 = Double.parseDouble(display);
                         percent = (num_1 * 100) / (50000000);
                    flip = 1;
                    catch(IOException e)
                    e.printStackTrace();
                    System.exit(1);
Now, when I run the script, I receive the following errors:
Exception occurred during event dispatching:
java.security.AccessControlException: access denied (java.io.FilePermission /Netadmin/UCDSNMP/bin/snmpdelta execute)
at java.lang.Throwable.fillInStackTrace(Native Method)
at java.lang.Throwable.fillInStackTrace(Compiled Code)
at java.lang.Throwable.<init>(Compiled Code)
at java.lang.Exception.<init>(Compiled Code)
at java.lang.RuntimeException.<init>(RuntimeException.java:47)
at java.lang.SecurityException.<init>(SecurityException.java:39)
at java.security.AccessControlException.<init>(AccessControlException.java:57)
at java.security.AccessControlContext.checkPermission(Compiled Code)
at java.security.AccessController.checkPermission(Compiled Code)
at java.lang.SecurityManager.checkPermission(Compiled Code)
at java.lang.SecurityManager.checkExec(SecurityManager.java:789)
at java.lang.Runtime.exec(Compiled Code)
at java.lang.Runtime.exec(Compiled Code)
at java.lang.Runtime.exec(Runtime.java:152)
at snmp.actionPerformed(Compiled Code)
at java.awt.Button.processActionEvent(Button.java:308)
at java.awt.Button.processEvent(Button.java:281)
at java.awt.Component.dispatchEventImpl(Compiled Code)
at java.awt.Component.dispatchEvent(Compiled Code)
at java.awt.EventQueue.dispatchEvent(Compiled Code)
at java.awt.EventDispatchThread.pumpOneEvent(Compiled Code)
at java.awt.EventDispatchThread.pumpEvents(Compiled Code)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:83)
The user is entering the parameters for the UNIX command from a Java applet. Everything looks right, but I can't seem to run the file? Please help! All is appreciated.
Jason Banks
Northeastern University

Sorry, this is a bug that I've reported -- see Sun's response and my original report (along with how to get around the problem) shown below:
Hi Vira Van.,
The bug you have reported is a duplicate of Bug ID: 4522533.
Thank you for providing us with additional information
that can be used in the resolution of this bug.
This bug can be monitored via the the Java Developer
Connection Bug Parade at:
http://developer.java.sun.com/developer/bugParade/index.jshtml
The Java Developer Connection is a free channel that is
maintained by staff here at Sun. Access this web page to join:
http://developer.java.sun.com/servlet/RegistrationServlet
The home page for the JDC is:
http://java.sun.com/jdc
Regards,
Girish
----------------- Original Bug Report-------------------
category : java
release : 1.4
subcategory : jar
type : bug
synopsis : signed applet: bad major version number on NN4.79 and ClassNotFound in IE5.5
description : FULL PRODUCT VERSION :
java version "1.4.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-b92)
Java HotSpot(TM) Client VM (build 1.4.0-b92, mixed mode)
FULL OPERATING SYSTEM VERSION : Windows 98 [Version
4.10.2222]
ADDITIONAL OPERATING SYSTEMS :
BROWSERS: Netscape Navigator 4.79
        : Internet Explorer 5.5
EXTRA RELEVANT SYSTEM CONFIGURATION :
Applet failed to start in Netscape, the following error
message appeared in the Java Console:
Netscape Communications Corporation -- Java 1.1.5
Type '?' for options.
Symantec Java! ByteCode Compiler Version 210.065
Copyright (C) 1996-97 Symantec Corporation
# Applet exception: error: java.lang.ClassFormatError: Bad
major version number
java.lang.ClassFormatError: Bad major version number
at java.lang.ClassLoader.defineClass(Compiled Code)
at netscape.applet.AppletClassLoader.findClass(Compiled
Code)
at netscape.applet.AppletClassLoader.loadClass1(Compiled
Code)
* at netscape.applet.AppletClassLoader.loadClass(Compiled
Code)
at netscape.applet.AppletClassLoader.loadClass(Compiled
Code)
at
netscape.applet.DerivedAppletFrame$LoadAppletEvent.dispatch(
Compiled Code)
at
java.awt.EventDispatchThread$EventPump.dispatchEvents(Compil
ed Code)
at java.awt.EventDispatchThread.run(Compiled Code)
at
netscape.applet.DerivedAppletFrame$AppletEventDispatchThread
.run(Compiled Code)
The same applet
A DESCRIPTION OF THE PROBLEM :
Unable to run signed applet with Netscape 4.79 and IE5.5
native JVM.
REGRESSION. Last worked in version 1.3.1
STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1.compile program and copy class files to a temp directory
2.sign the applet for Netscape as follows:
signtool -k aok -d \progra~1\netscape\users\viravan -Z
FIO.jar temp
3.sign the applet for Internet Explorer as follows:
cabarc -p n FileIO.cab FileIO*.class
setreg 1 true
makecert -sk aok -n "CN=aok" aok.cer
cert2spc aok.cer aok.spc
signcode -j javasign.dll -jp LOWX -spc aok.spc -k aok
FileIO.cab
Run the applet with the following HTML file:
<html><head><Title>Self-Signed Applet</Title>
<script>
document.layers ? parm=1 : parm=0;
</script>
<body>
This file I/O applet lets you read and write to the user's
local disk.<br>
<br>
<script>
document.writeln('<APPLET CODE = "FileIO" CODEBASE = "."
ARCHIVE = "FIO.jar" WIDTH = 10 HEIGHT = 10 NAME = "JSF">');
document.writeln('<param name="Netscape"
value="'+parm+'">');
document.writeln('<param name="cabbase"
value="FileIO.cab">');
document.writeln('</APPLET>');
</script>
</body>
</html>
EXPECTED VERSUS ACTUAL BEHAVIOR :
A frame with a textarea and some buttons should popup in the
center of the screen.
ERROR MESSAGES/STACK TRACES THAT OCCUR :
Applet signed with signtool failed to start in Netscape, the following error
message appeared in the Java Console:
Netscape Communications Corporation -- Java 1.1.5
Type '?' for options.
Symantec Java! ByteCode Compiler Version 210.065
Copyright (C) 1996-97 Symantec Corporation
# Applet exception: error: java.lang.ClassFormatError: Bad major version number
java.lang.ClassFormatError: Bad major version number
at java.lang.ClassLoader.defineClass(Compiled Code)
at netscape.applet.AppletClassLoader.findClass(Compiled Code)
at netscape.applet.AppletClassLoader.loadClass1(Compiled Code)
* at netscape.applet.AppletClassLoader.loadClass(Compiled Code)
at netscape.applet.AppletClassLoader.loadClass(Compiled Code)
at netscape.applet.DerivedAppletFrame$LoadAppletEvent.dispatch(Compiled Code)
at java.awt.EventDispatchThread$EventPump.dispatchEvents(Compiled Code)
at java.awt.EventDispatchThread.run(Compiled Code)
at netscape.applet.DerivedAppletFrame$AppletEventDispatchThread.run(Compiled
Code)
The same applet signed with signcode failed to start in Internet explorer, the
error message in the Java Console is:
Error loading class: FileIO
java.lang.NoClassDefFoundError
java.lang.ClassNotFoundException: FileIO
        at com/ms/vm/loader/URLClassLoader.loadClass
        at com/ms/vm/loader/URLClassLoader.loadClass
        at com/ms/applet/AppletPanel.securedClassLoad
        at com/ms/applet/AppletPanel.processSentEvent
        at com/ms/applet/AppletPanel.processSentEvent
        at com/ms/applet/AppletPanel.run
        at java/lang/Thread.run
This bug can be reproduced always.
---------- BEGIN SOURCE ----------
import java.io.*;
import java.util.*;
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class FileIO extends Applet implements ActionListener {
   public static void main(String[] args) {
      new FileIO();
      F.addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent e) {
            System.exit(0);
   public void init() {
      String tmp=getParameter("Netscape");
      if (tmp!=null) {
         if (tmp.equals("1")) {
            try {
netscape.security.PrivilegeManager.enablePrivilege("UniversalFileAccess");
               NS=true;
            } catch (Throwable exception) {}
      new FileIO();
      F.setResizable(false);
   public void stop() {
      F.dispose();
   public FileIO() {
      newline=System.getProperty("line.separator");
      F.setLayout(new BorderLayout(0,0));
      String line,inbuf="";
      String newline=System.getProperty("line.separator");
      text=new TextArea(inbuf,24,80,TextArea.SCROLLBARS_BOTH);
      text.setFont(new Font("Courier",Font.PLAIN,12));
      text.setBackground(Color.cyan);
      text.setForeground(Color.black);
      F.add("Center",text);
      Panel pan=new Panel();
      pan.setLayout(new FlowLayout(1,0,0));
      pan.setBackground(Color.yellow);
      TF=new TextField(40);
      TF.setFont(new Font("Courier",Font.PLAIN,12));
      pan.add(TF);
      OP=new Button("Open");
      OP.addActionListener(this);
      pan.add(OP);
      FS=new Button("Save");
      FS.addActionListener(this);
      pan.add(FS);
      SA=new Button("Save-As");
      SA.addActionListener(this);
      pan.add(SA);
      reset=new Button("Reset");
      reset.addActionListener(this);
      pan.add(reset);
      F.add("South",pan);
      F.pack();
      Dimension screen=Toolkit.getDefaultToolkit().getScreenSize();
      Dimension size=F.getSize();
      int X=(screen.width-size.width)/2;
      int Y=(screen.height-size.height)/2;
      F.setLocation(X,Y);
      F.setVisible(true);
   public void actionPerformed(ActionEvent event) {
      String tmp="";
      String O=text.getText();
      StringTokenizer tkn=new StringTokenizer(O,newline);
      int ntkn=tkn.countTokens();
      Object ev=event.getSource();
      if (ev.equals(OP)) {
         FileDialog fd=new FileDialog(F,"File to open",FileDialog.LOAD);
         fd.setFile("*.java");
         fd.show();
         tmp=fd.getDirectory();
         if (fd.getFile()==null) {text.requestFocus(); return;}
         tmp+=fd.getFile();
         TF.setText(tmp);
         try {
            if (NS)
{netscape.security.PrivilegeManager.enablePrivilege("UniversalFileRead");}
            BufferedReader reader=new BufferedReader(new FileReader(tmp));
            String line;
            String crlf="";
            tmp="";
            while ((line=reader.readLine())!=null) {
               tmp+=crlf+line;
               crlf="\n";
            reader.close();
            text.setText(tmp);
         } catch (Throwable e) {
            e.printStackTrace();
      } else if (ev.equals(FS) || ev.equals(SA)) {
         try {
            if (ev.equals(SA)) {
               FileDialog fd=new FileDialog(F,"File to save",FileDialog.SAVE);
               fd.setFile("*.java");
               fd.show();
               tmp=fd.getDirectory();
               tmp+=fd.getFile();
            } else {
               tmp=TF.getText();
            if (tmp.length()==0) {text.requestFocus(); return;}
            if (tmp.indexOf(".java")<0) tmp+=".java";
            TF.setText(tmp);
            if (NS)
{netscape.security.PrivilegeManager.enablePrivilege("UniversalFileWrite");}
            FileOutputStream fos=new FileOutputStream(tmp);
            BufferedWriter out=new BufferedWriter(new OutputStreamWriter(new
DataOutputStream(fos)));
            for (int i=0;i<ntkn;i++) out.write(tkn.nextToken()+newline);
            out.flush();
            out.close();
            if (NS)
{netscape.security.PrivilegeManager.revertPrivilege("UniversalFileWrite");}
            System.out.println(tmp+" saved");
         } catch (Throwable e) {
            e.printStackTrace();
      } else if (ev.equals(reset)) {
         text.setText("");
         TF.setText("");
      text.requestFocus();
   private String replace(String input, String srch, String repl) {
      int i=input.indexOf(srch);
      while (i>=0) {
         input=input.substring(0,i)+repl+input.substring(i+srch.length());
         i=input.indexOf(srch);
      return input;
   private Button OP,FS,SA,reset,TB;
   private boolean newLine,NS=false;
   private TextArea text;
   private TextField TF;
   private final char NL='\n';
   private String content,newline;
   private static Frame F=new Frame("FileIO");
---------- END SOURCE ----------
CUSTOMER WORKAROUND :
build the signed applet with SDK1.3.1 or make it a signed
applet that uses Java Plugin 1.4.0 (i.e., sign it with jarsigner).
workaround :
suggested_val :
cust_name : Vira Van.
dateCreated : 2002-03-24 19:52:18.4
dateEvaluated : 2002-04-01 18:48:10.858

Is it possible to run all Dos based command on Java ?

hello friends
I run Dos Commands on Java by following code
try{
Process p=Runtime.getRuntime().exec(new String[]{"cmd.exe","/c","dir"});
}catch(Exception e){e.printStackTrace();}
System.out.println("bye");
If I run "mkdir" instead of "dir" folder is created in current directory. But in case of "dir" listing of file folders is not displayed to me . means "dir " is not running.
could any body tell me what to do in this case
thanks

ejp wrote:
'dir' is not an executable program. It is built-in to the command shell. The only way you can execute it is by feeding it to a shell via a batch file.Sorry 'ejp' but 'dir' can be run this way (I have just checked on XP) so there has to be something wrong with the way the OP is processing the results. Since he does not seem to process stdout or stderr and he does not wait for the process to complete I am betting he is falling foul of one or more of the traps. My best bet is that he is expecting a console window to open and the directory listing to appear in it.

How to execute dos command in Java program?

In Perl, it has System(command) to call dos command.
Does java have this thing?
or any other way to execute dos command in java program?
Because i must call javacto compile a file when the user inputed a java file name.

Look in the Runtime class, it is implemented using the Singleton design pattern so you have to use the static method getRuntime to get its only instance, on that instance you can invoke methods like
exec(String command) that will execute that command in a dos shell.
Regards,
Gerrit.

Running unix command using java shows error

Hi All,
I am trying to run UNIX move command using Java exec method but its throwing error, unable to rename. Here below is the code i am trying to run to move all files from one directory to another directory. source and destination directory exists.
public class Demo
    public static void main(String args[])
        try
            Runtime rt = Runtime.getRuntime();
            Process proc = rt.exec("mv /home/demo1/* /home/demo2");
            int exitVal = proc.waitFor();
            System.out.println("Process exitValue: " + exitVal);
        } catch (Throwable t)
            t.printStackTrace();
}if i give "mv /home/demo1 /home/demo2" in exec method, its working, with * character its giving problem.
Please help me in resolving the problem.
Thank you

Characters like *, >, &, |, etc. are interpreted by the command shell--that is by the bash, zsh, etc. programs. When you execute a command with ProcessBuilder or Runtime.exec, you're not going through one of those shells, so their interpretation of those characters is not available.
In your code, the character * is being delivered directly to the mv command (which doesn't think * is anything special), as opposed to being turned into a list of files and directories as it would be when it's interpreted by the shell. The mv command doesn't know anything about the * character being special.
If you want to have those shell interpretations, you need to execute the command through a shell. One example is like so, but a) you'll want to read up on the methods in exec() that take arrays of String, and b) you'll want to read up on ProcessBuilder, and c) you'll need to check your shell's man pages to see the exact syntax and arguments.
runtime.exec("/bin/bash -c 'mv x/* y'");

Running ls command from Java stroed procedure no output

Hi ,
I am trying to run ls command from java stored procedure in oracle
Process p = Runtime.getRuntime().exec("ls");
BufferedReader stdInput = new BufferedReader(new
InputStreamReader(p.getInputStream()));
BufferedReader stdError = new BufferedReader(new
InputStreamReader(p.getErrorStream()));
// read the output from the command
System.out.println("output of the command run:\n");
while ((s = stdInput.readLine()) != null) {
System.out.println(s);
from java stored procedure in oracle.
i get output of println statments but it does not go into while loop to print from stdInput.
Result of running Java stored procedure is -
output of the command run:
Call completed.
when i run the program on client side it works fine.
Has anybody tried this from java stroed procedure.
Thanks,
Jag

Jag,
Actually, the question of whether it works for me seems to depend on the version of the OS (or Oracle). On RedHat Linux (Oracle 8.1.6) it didn't work at all, but on Solaris (Oracle 9.0.2) it did. Here's the output from that run:
SQL> /
output of the command run:
init.ora
initDBPart9i.DBPSun01.ora
initdw.ora
lkDBPART9I
orapw
orapwDBPart9i
spfileDBPart9i.ora
Done
PL/SQL procedure successfully completed.
But, I did need to change a line of your code to this:
Process p = Runtime.getRuntime().exec("/usr/bin/ls");
your original was:
Process p = Runtime.getRuntime().exec("ls");
You might consider, if possible, use of some of the Java File classes instead of ls, as this might make things more predictable for you. There were some examples in oramag.com a few months ago, but they were pretty simple (you might not need them).
Hope this helps,
-Dan
http://www.compuware.com/products/devpartner/db/oracle_debug.htm
Debug PL/SQL and Java in the Oracle Database

How can I run Runtime.exec command in Java To invoke several other javas?

Dear Friends:
I met a problem when I want to use a Java program to run other java processes by Runtime.exec command,
How can I run Runtime.exec command in Java To invoke several other java processes??
see code below,
I want to use HelloHappyCall to call both HappyHoliday.java and HellowWorld.java,
[1]. main program,
package abc;
import java.util.*;
import java.io.*;
class HelloHappyCall
     public static void main(String[] args){
          try
               Runtime.getRuntime().exec("java -version");
               Runtime.getRuntime().exec("cmd /c java HelloWorld "); // here start will create a new process..
               System.out.println("Never mind abt the bach file execution...");
          catch(Exception ex)
               System.out.println("Exception occured: " + ex);
} [2]. sub 1 program
package abc;
import java.util.*;
import java.io.*;
class HelloWorld
     public static void main(String[] args){
     System.out.println("Hellow World");
} [3]. Sub 2 program:
package abc;
import java.util.*;
import java.io.*;
class HappyHoliday
     public static void main(String[] args){
     System.out.println("Happy Holiday!!");
} When I run, I got following:
Never mind abt the bach file execution...
I cannot see both Java version and Hellow World print, what is wrong??
I use eclipse3.2
Thanks a lot..

sunnymanman wrote:
Thanks,
But How can I see both programs printout
"Happy Holiday"
and
"Hello World"
??First of all, you're not even calling the Happy Holiday one. If you want it to do something, you have to invoke it.
And by the way, in your comments, you mention that in one case, a new process is created. Actually, new processes are created each time you call Runtime.exec.
Anyway, if you want the output from the processes, you read it using getInputStream from the Process class. In fact, you really should read that stream anyway (read that URL I sent you to find out why).
If you want to print that output to the screen, then do so as you'd print anything to the screen.
in notepad HelloWorld.java, I can see it is opened,
but in Java, not.I have no idea what you're saying here. It's not relevant whether a source code file is opened in Notepad, when running a program.

How to use cvs checkout command in java

Hi,
I am using Ubuntu
I have installed cvs client in ubuntu
I have one problem running 'cvs checkout' command through java..
"cvs" -d ":ext:[email protected]:/var/cvs" co -P "Auto/test"
When i run the above command in terminal, i got one prompt like '[email protected]'s password:' in the terminal if i give the valid password the folder 'Auto' checked out successfully..
I have tried following steps but i don't know how to give the password to the terminal using java
First i created the 'checkout.sh' file.
In this i have typed "cvs" -d ":ext:[email protected]:/var/cvs" co -P "Auto/test"
Then i call it using java by the following code
=================================================================
String cmd[] = {"bash","checkout.sh"};
Runtime.getRuntime().exec(cmd).waitFor();
=================================================================
Anyone let me know how do I achieve this in java?
Thanks in Advance
Kulandaivelu

masijade. wrote:
PhHein wrote:
Maybe you need to modify your links to be more obvious :P
[*>>klick me<<*|http://www.jcvs.org/]
Nah! Attention to detail is one of most crucial attributes for a programmer in any language. ;-)
Edit: The urls seemingly don't like h1 and color tags. ;-)Nope, they don't and I couldn't be bothered to try.
Gratz on Gold!

How to execute a shell command in java?

here, my environment is redhat 7, jdk 1.5.
i don't know how to use the shell command in java.
i want to use this function:
#include <stdlib.h>
int system(const char * string);
please give me some ideas. and Thank you so much if coming with a little demo.

i know i should use JNI. because i have to use C lib.
but i have already use JNI to wrapper the original code the cpp code and java code is :
//: appendixb:UseObjImpl.cpp
//# Tested with VC++ & BC++. Include path must
//# be adjusted to find the JNI headers. See
//# the makefile for this chapter (in the
//# downloadable source code) for an example.
#include <jni.h>
#include <stdlib.h>
extern "C" JNIEXPORT void JNICALL
Java_UseObjects_changeObject(
JNIEnv* env, jobject, jobject obj) {
jclass cls = env->GetObjectClass(obj);
jfieldID fid = env->GetFieldID(
cls, "aValue", "I");
jmethodID mid = env->GetMethodID(
cls, "divByTwo", "()V");
int value = env->GetIntField(obj, fid);
printf("Native: %d\n", value);
env->SetIntField(obj, fid, 6);
env->CallVoidMethod(obj, mid);
value = env->GetIntField(obj, fid);
system("preprocess -path sha.c");
printf("Native: %d\n", value);
} ///:~
//: appendixb:UseObjects.java
// From 'Thinking in Java, 2nd ed.' by Bruce Eckel
// www.BruceEckel.com. See copyright notice in CopyRight.txt.
class MyJavaClass {
public int aValue;
public void divByTwo() { aValue /= 2; }
public class UseObjects {
private native void
changeObject(MyJavaClass obj);
static {
// System.loadLibrary("UseObjImpl");
// Linux hack, if you can't get your library
// path set in your environment:
System.load(
"/root/jproj/UseObjImpl.so");
public static void main(String[] args) {
UseObjects app = new UseObjects();
MyJavaClass anObj = new MyJavaClass();
anObj.aValue = 2;
app.changeObject(anObj);
System.out.println("Java: " + anObj.aValue);
} ///:~
i modify this two file which is from TIJ-2edition.
the output is
Native: 2
Native: 3
Java: 3
but what i want to be executed "preprocess -path sha.c" does not work.
i have change the command to, such as "df", "ls" etc. but none of them works
please help me.

Using the "java" command in Java 1.4.1

Hello..
I don't seem to be able to run any application that should run with
the "java" command in Java 1.4.1. Everytime I use "java" I get the "java.lang.NoClassDefinitionError"
Even running this simple program doesn't work:(
package chapter10;
public class test {
public static void main(String args[]) {
System.out.println("Hello WORLD!!");
}//end class
when I run: "java chapter10/test"
I get the following message:
"Exception in thread 'main' java.lang.NoClassDefinitionError: chapter10/test"
And the sam happens to any other class when I try to run it:(
The "javac" command works fine:) but the "java" is giving me a hard time:(
I would appreciate any suggestions or answers to this problem:) THANK U

See if this explanation helps.
Assume that your programs are part of a package named divelog, which is specified by the first line in each source file: package divelog;
Also assume that this directory (C:\javaT\myWork\) is part of the CLASSPATH list of directories.
Also assume that all the source files reside in this directory structure: C:\javaT\myWork\divelog\
Then a statement to compile a source file Named Divelog.java is:
C:\JavaT\myWork\>javac divelog\Divelog.java
Explanation:
Java starts looking for classes in the directory(s) listed in the classpath. In this case, one of the directories should be: C:\JavaT\myWork\ since it contains your divelog package.
Compiling
A class can either be part of a package (ie, no package statement at the top of the class.), or not.
If the class is not part of a package: Its source file needs to be in one of the classpath directories. To compile you use the command: javac SomeFile.java, from within the classpath directory that contains the file.
The class is part of a package (this case): The source file must be in a subdirectory structure that starts in one of the classpath directories. The subdirectory structure must match the package statement.
So, you generate a directory structure C:\javaT\myWork\divelog\ which is the [classpath directory + the package subdirectory structure], and place Divelog.java in it.
Then from the classpath directory (C:\JavaT\myWork\) use the command: javac divelog\Divelog.java
This creates a file, Divelog.class in the divelog directory. (The following is where people tend to get lost.) The correct name now, as far as java is concerned, is the combination of package name and class name: divelog.Divelog (note I omit the .class)
Running
To run a class that's not part of a package: From within the classpath directory that contains the class. use the command: java SomeFile
To run a class that is part of a package: From within the classpath directory (C:\JavaT\myWork\) use the command java divelog.Divelog (Note that this is analogous to the command for a class not in a package, you just use the fully qualified name)

Trying to compile a .java file from another .java file

Hello,
I'm trying to compile a .java file from another .java file using Runtime.exec...
String c[]=new String[3];
c[0]="cmd.exe"; c[1]="/c" ; c[2]="javac Hello.java";
Process p=Runtime.exec(c);
If anyone can help me in atleast getting the command prompt when Runtime.exec("cmd.exe") is executed...that would be great...I tried out notepad.exe, calc, explorer instead of cmd.exe...all the commands display their respective windows..except cmd.exe...the command prompt doesnt appear...
Please help me ASAP....
Thanks for your help in advance...
Regards.
AKhila.

try this. ur code will be compliled and will get .class file. but console won't appear. is it a must for u?
public class Exec{
     public static void main(String a[]) throws Exception{
          String c[]=new String[3];
          c[0]="cmd.exe"; c[1]="/c" ; c[2]="javac Hello.java";
          Process p=Runtime.getRuntime().exec(c);
          // or Runtime.getRuntime().exec("javac Hello.java");

How to call a html file in a java file

how to call a html file inside a java file ?

Hopeless. Are you by any chance a rare gas? You seem completely inert. LOL You totally pwned him there :rolls eyes:
well, no, I think he's looking for something to this degree:
in HTML, there is a mailto: command that makes the system default handled way to email emails open up. He's looking for a command thats very nice and opens a html file in the system default browser.
So, Dick, Runtime.exec would work execpt that he needs a way to find the default system browser to call exec on, AND he has to know how to pass html file locations to the executable via command line arguments
He just didnt try to phrase it at all :P

Calling CL command in java

I would like to know how to call cl command in java to delete a file in my server. thanks

Use the java.lang.Runtime interface. The exec() method allows you to execute commands from the command shell:
String cmd = new String[2];
cmd[0] = "cl";
cmd[1] = fileToDelete;
Runtime rt = Runtime.getRuntime();
rt.exec(cmd);

File command in Java

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