Running a Linux command "clear" from a Java program

Hello. How to run a simple linux command to clear the screen from a Java program. I did the following
Process p = Runtime.getRuntime().exec("clear");
Nothing is happening.

you're not supposed to mess with the shell, youdon't own it and
shouldn't try to dictate what happens with it.
The shell is a multiuser system,What?
The command shell (for example sh, ksh, bash, csh,
zsh) is a process, a command interpeter just like any
other (user mode) program.
yes, and there can be multiple processes writing to it at any one time.
You do NOT have exclusive access to it, nor should you ever assume you do.
In a multiuser system there can be several shells
running on behalf of several users. The same user can
run several shells.
Yes, and each shell can be accessed by multiple processes at any one time.
So what?
Process a writes to the shell.
Process b writes to the shell.
Process a clears the shell, removing whatever process b wrote there.
You've just messed up process b, or at the very least its output.
Do NOT assume you have exclusive access to any shell.

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How to Create Linux-Cron Job from a Java Program

Hello,
Can anybody help me to CREATE/EDIT/DELETE Linux Cron job from Java Program. Its Very Urgent.Thanks in advance..
from
Chakri

I decided this didn't sound too tough so I played around with it a little. Basically because I'd never tried executing external processes out of java before, so I wanted to see how it was done.
Just change whatever you like in the jobs ArrayList and call writeJobs.
If you call writeJobs without putting anything in the list first you'll wipe out all of your crontab entries.
import java.lang.*;
import java.io.*;
import java.util.*;
public class cron {
    ArrayList jobs;
    Runtime rt;
    cron() {
     rt = Runtime.getRuntime();
     jobs = new ArrayList();
    void readCron() {
     String[] list = { "crontab", "-l" };
     jobs = new ArrayList();
     try {
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         Process child = rt.exec(list);
         BufferedReader cronout = new BufferedReader(new InputStreamReader(child.getInputStream()));
         String cronjob = cronout.readLine();
         while (cronjob != null) {
          jobs.add(cronjob);
          cronjob = cronout.readLine();
         child.waitFor();
     catch(IOException e) {
         System.err.println("IOException starting process!");
     catch(InterruptedException e) {
         System.err.println("Interrupted waiting for process!");
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     Iterator iter = jobs.iterator();
     while (iter.hasNext()) {
         System.out.println((String)iter.next());
    void writeJobs() {
     String[] edit = { "crontab"};
     try {
         // Stick a job into crontab
         Process child = rt.exec(edit);
         PrintWriter cronIn = new PrintWriter(child.getOutputStream());
         Iterator iter = jobs.iterator();
         while (iter.hasNext()) {
          cronIn.println((String)iter.next());
         cronIn.close();
         child.waitFor();
     catch(IOException e) {
         System.err.println("IOException starting process!");
     catch(InterruptedException e) {
         System.err.println("Interrupted waiting for process!");
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How to run a cygwin.bat from a java program?

Can you please let me know how to run a cygwin.bat file from a java program and to give commands through java program. I have a program to run .exe files, but when I do the same for the cygwin.bat it doesnt work. In task mgr a BASH and a cmd.exe is running. Please help me on this & bit urgent. Thanks in advance!

Can you please let me know how to run a cygwin.bat
file from a java program and to give commands through
java program. I have a program to run .exe files, but
when I do the same for the cygwin.bat it doesnt work.Of course not. .bat files are no native executables. You need to open a shell first, like "cmd /c cygwin.bat ..."
& bit urgent. Thanks in advance!If I had read this earlier I wouldn't have replied. Why exactly is your time worth more than anybody else's?

How can i run a linux command in java app?

i created a cell script to run the compile process of my C++ simulator and want to control it thru java application, i tried the following but it doesn't work.
the command in linux should be. under the path /home/workspace/SIM/ run: . / zs_compile
and i use runtime to do this
String path="home/workspace/SIM/ . /zs_compile";
try {Runtime.getRuntime().exec(path);}
catch( IOException e) {
e.printStackTrace() ;
Error report is java.io.IOException: java.io.IOException: home/workspace/SIM/ . /zs_compile : not found
who can help me to find the reason, thanks a lot!!!!!

the reason is that the command you're truing to execute can't be found. se this article for other traps relatd to runtime.exec:
http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html
the command in linux should be. under the path /home/workspace/SIM/ run: . / zs_compilecould yu elaborate a bit? "should be . under the path" -- do you mean it should be sourced from that path? Sourcing a script file makes no sense from a Java program.

Running curl command from a java program using Runtime.getRuntime.exec

for some reason my curl command does not run when I run it from within my java program and errors out with "https protocol not supported". This same curl command however runs fine from any directory on my red hat linux system.
To debug the problem, I printed my curl command from the java program before calling Runtime.getRuntime.exec command and then used this o/p to run from the command line and it runs fine.
I am not using libcurl or anything else, I am running a simple curl command as a command line utility from inside a Java program.
Any ideas on why this might be happening?

thanks a lot for your response. The reason why I am using curl is because I need to use certificates and keys to gain access to the internal server. So I use curl "<url> --cert <path to the certificate>" --key "<path to the key>". If you don't mid could you please tell me which version of curl you are using.
I am using 7.15 in my system.
Below is the code which errors out.
public int execCurlCmd(String command)
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                 // read the output from the command
                 System.out.println("Here is the standard output of the command:\n");
                 while ((s = stdInput.readLine()) != null) {
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                 while ((s = stdError.readLine()) != null) {
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                 return(0);
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How to execute unix command from the Java program running on Windows

Hello,
I need to
1. Execute a unix shell script from a Java program running on the Windows.
2. I also need to capture the output of this shell script in my program.
Please suggest me how to achieve this.
Thanks in Advance.

Hi...
Something is missing here
If you want to execute a shell script in windows that not posible unless you find or develop a unix shell script parser for windows.
But if you are trying the execute a unix shell script on a remote unix computer from your java program running on a windows platform you can do that by logging on to the UNIX terminal which is running on port 23 I think.
You can test this using telnet tool on windows
just type on command prompt
telnet <ip of the unix pc> <port number this case 23>
you should get the unix terminal. If that works you can do the same through java or you can directly conect to port 23 of that pc using sockets that way your program will be platform independant

How to run a openssl command from a java program

Hi All
Please suggest on how to run a openssl command from a java program.
I am using this
Runtime runtime = Runtime.getRuntime();
runtime.exec("openssl pkcs8 -inform der -nocrypt test.der result.pem");
This is suppose to take test.der as input and create result.pem.
There are no errors but the file result.pem isnt created.
Thanks in Advance

First off is that openssl command correct? Should it be this instead:
openssl pkcs8 -inform der -nocrypt -in test.der -out result.pem
Try out your openssl command within a command prompt so that you know that it works ok. I think the command line you specified waits on stdin (well it does for me).
After that.....
runtime.exec creates a Process object. If you do this:
Process openssl = runtime.exec("....")
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Alternatively you could get the stderr from the process and look inside it - if it is 0 length then all is good, if it has some text in there then it has likely failed. You could then throw an exception and include the stderr output in the exception messgae. You may need to experiment with this, runnig it first when openssl is happy then running it again when openssl is upset.
M

How to compile and run a .java file from another java program

hello,
can any one tell me how to compile and run a *.java* file from another java program which is not in same directory?

Well a smarter way of implementing this is by using a solution provided by Java Itself.
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http://java.sun.com/javase/6/docs/api/javax/tools/package-summary.html
How do i do that ??
Check out the below articles which would help you of how to do that
http://www.ibm.com/developerworks/java/library/j-jcomp/index.html
http://www.javabeat.net/javabeat/java6/articles/java_6_0_compiler_api_1.php
http://books.google.com/books?id=WVbpv8SQpkEC&pg=PA155&lpg=PA155&dq=%22javax+tools%22+compiling+java+file&source=web&ots=XOt0siYe-f&sig=HH27ovuwvJgklIf8omTykUmy-eM
Now once we are done with compilation.In order to run a Specific class all you ought to do is create an object and its specific methods of a specified class included in the CLASSPATH which you can manage it easily by usage little bit reflections.
Hope that might help :)
REGARDS,
RaHuL

How can I pass system commands from a java program? Urgent!

hi,
I have been trying this out since a long time. How do I send system commands to command.com or cmd.exe from a java program and an output of the executed command back to the java application.
If u have any idea, or have any information about the kind os application reply back.
Thanks
Deepa Datar

This is the code which I tried, but it displays only the title of MS-DOS, something like " Microsoft Corp...etc ". But doesn't take any input, and the subprocess(cmd.exe) hangs.
import java.io.*;
public class cmddemo2
public static void main(String arg[])
try
System.out.println("cmd");
Process p=Runtime.getRuntime().exec("cmd.exe");
DataInputStream din=new DataInputStream(p.getInputStream());
DataOutputStream dout=new DataOutputStream(p.getOutputStream());
System.out.println("after streams");
String s;
dout.writeChars("type cmddemo2.java");
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while((s1=din.readLine())!="\n")
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{ System.out.println("Exception : "+e);

Execute several UNIX OS commands from inside Java program

Greetings,
I would like to be able to execute from a Java program several of the following UNIX commands
script filename
cd
date
grep
diff
I have been able to get a single command to work with
Runtime rt = Runtime.getRuntime();
Process p = rt.exec("dir");
My goal here is to accomplish a Java program which will use JDBC to access an Oracle database with SQL and then compare the resultant flat file with a diff command in Unix to another delimited file from an Excel spreadsheet. Your input is appreciated.
Thank you

I would suggeat to use JDBC to get the data from database and then read your file and then use existing java diff program from following link to find the differences between the files
http://www.bmsi.com/java/
I hope this helps
VAN

How:Execute OS commands from a Java program

hi,
is it possible to execute an OS command from a java program, as in C/C++? if yes, plz give the details.
thanx

In the future try searching the forum before posting. Using keywords like "execute os commands" would lead you to several postings on this topic.
Note the keywords where taken directly from you subject line. With practice you learn which keywords to use to yield the best search results.

How to run a remote application (Non Java) from a Java program

Could you please tell me how to run a remote application (Non-Java) from a Java program without using RMI. Please tell me know the procedure and classes to be used.
Cheers
Ram

what do you mean remote application.In the other pc or in your pc just apart from you application?
If the application is in your pc,the method which the upper has mentioned is
a good one!
But if the application you want to run is not in your computer,the method can't do. And you can use socket with which you can build an application listening some port in the pc which contains the application you want to run .When you want to run that application ,send the Start_Command to the listening application.Then listening application will run the application with the help of the method the upper mentioned.

How to run a CMD command directly from run ?

How to run a CMD command directly from run ?
Like "cmd md D:\abcd". I did this before. But now I totally forgot how to do that ?
Please help..........

Hi,
To add, here is the command CMD reference:
Cmd
Best regards
Michael Shao
TechNet Community Support

Sending POSIX signal to an external subprocess from a java program

I'm programing in forte for java under linux-mandrake, I've execute an external subprocess with the runtime and Process clases, I need to send the 2� POSIX signal to this external subprocess, I mean de SIGINT signal, I know that you can send a signal from a shell just doing:
Kill -2 pid // the SIGINT signal is the 2 POSIX signal
I know that there is another system-call like : kill(int signal, int pid) that any one can send from a c program.
Althought I don't know how can I get the pid of a suprocess, because I Know that there is the systemcall in c like:
int getpid() wich gives the pid of the current process, but I need to have the pid of a subprocess not the current one.
The thing is that I do not know how can I do it from a java program, I mean that to send a signal to a subprocess it will work using system-calls, but I do not know if I can insert system call in a java program, I've been thinking about doing it using a linux script like:
#!bin/bash
$a = pidof /home/maude-linux/bin/maude.linux
# this is the path of the process wich is running
kill -2 a$
and the run this script from a java program doing an exec(sh script.bin)
but by the moment I must be doing something wrong in the script because I find mistake in it, it gives me mistake in the assign sentence , I mean:
$a = pidof /home/maude-linux/bin/maude.linux
# this is the path of the process wich is running
I'm not used to program shell scripts, perhaps I'm doing something wrong, is there something wrong in this sentence?.
I would aprecciate some help about this, or if somebody have some idea how to do it in java, I repeat I need to send a signal to a external subprocess wich is launched from a java program by the process and runtime clases, and I need to send a SIGINT signal to the subprocess, I hope that some body can give some suggestion or some code explaining the situation

Are the portions of bash-code verbatim in your post?
When yes, they look suspicious!
Instead of
#!bin/bash
#!/bin/bash
would be better.
$a = pidof /home/maude-linux/bin/maude.linux
does not look good either.
If you have command "pidof" telling the pid based on the path name of the executable passed to it as its argument, you can have the output of this program in a shell script like this:
a=$( pidof /home/maude-linux/bin/maude.linux )
Then through $a you will refer to the value of the variable "a":
kill -SIGINT $a
A pidof script could look like this (apart from error handling):
ps -ef|awk '{if (NF>=8 && $8=="'"$1"'") print $2;}'
This works for me; your mileage may vary.

Need to execute tcl script from a Java Program

Hello,
I need to execute a tcl script from a Java Program. But I do not know how to call the tcl Interpreter. Can anybody help me?

Iam using the exec command as follows:
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ctcl.exe C:/Hello.tcl");
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And what is the return code from running it?

Running a Linux command "clear" from a Java program

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