Calling external applications from within a script.

Whenever I write scripts that require some external application for functionality, I try to open a pipe or start a server so that I only have to start the external application once. I expect that to reduce overhead and consider it good form. However, sometimes there just isn't any way to avoid calling an external application multiple times and when that happens, I try to find some other workaround if I think it's going to get called repeatedly.
What I'm wondering is how much it really matters for very small and simple programs. The one I have in mind right now is "du". I need to use it in a Perl script because Perl's operators to get file sizes return the apparent size which, in this case, is much larger than the actual size reported back by "du". I'm monitoring the size of files in real-time and I need to call "du" during each iteration of the status updater. Even though I'm passing all the file paths at once, "du" may be called a few times every second (well, I could limit it to once a second).
Could this possibly make any noticeable different on older machines? In general, what external apps can you get away with calling repeatedly?

I'm not sure, but I thing that overhead caused by calling du cannot be big enough to matter even on older machines.
But, when calling du from Perl script you are also invoking shell, and this can be a little bit more 'heavy'.

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It's possible to include hyperlinks in an InDesign file and export them in an EPUB file. Since I'm not familiar with working with SSH clients (in fact, I just had to Google it to have a clue what you're talking about), is this something that can be invoked in a standard URL format? If so, you could probably include it.
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I've got a fairly complex existing Tomcat application (which is packaged and built as a .war file) which I'm trying to edit so that it calls a Perl script part way through the processing, which will generate an XML file used later on. I think I've worked out how to call external scripts from within Java, but at the moment when I try and access the application via Tomcat the application either hangs or bails out (I don't know which, as the log files unhelpfully don't give any error messages).
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I'm not sure, but I thing that overhead caused by calling du cannot be big enough to matter even on older machines.
But, when calling du from Perl script you are also invoking shell, and this can be a little bit more 'heavy'.

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I am new to BPM 11g and need to create the ability to call an external application (UCM) from within BPM. Will a web service adapter, with a type of Reference, accomplish this? How can I add security to this web service.
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Hi Randy,
You can call an external application using a spring component integration, I was just able to get that to work with a help from another forum member here is a viewlet that demos the spring integration:
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To contact 3rd party application from within EJB container

What are the possible options to communicate with an external application from within EJB container? Options that I can think of are
- RMI
- JMS
- Socket communication
- HTTP
- any other option???
And if anyone can give the pros & cons of the different approaches, based on their experiences it will be great.

Hi,
There is one more.
Web Services which is much powerful than any other.
Ofcourse for this also u have to use socket communication and http protocol.
SOAP(Simple Object Access Protocol).. I think u got it..
I prefer SOAP as it has many adavantages over RMI and other.
Thanks,
All the best.
What are the possible options to communicate with an
external application from within EJB container?
Options that I can think of are
- RMI
- JMS
- Socket communication
- HTTP
- any other option???
And if anyone can give the pros & cons of the
different approaches, based on their experiences it
will be great.

Calling external programs from Java?

Hi All,
Is there a way of calling external applications from Java without using Runtime.exec(). That method seems quite messy when you are dealing with streaming data from an input file to an output file. Basically what I'm asking is there a way to run a command the same way you would type it in a command shell?
Thanks

LeWalrus wrote:
Ok, I've an external application that I want to be called inside a Java GUI. It has several input arguements, which the format looks something like:
programname inputfile > outputfile
Simple enough.
>
Works fine from a shell command line. From what I understand, this won't work using Runtime.exec() because that method will just start the application. Works fine from Runtime.exec(). Since you are'>' to write stdout to a file you need to us a shell to execute the command.
String[] command = {"sh", "-c","programname inputfile > outputfile"};
Process process = runtime.exec(command);
You need to read, digest and implement the recommendations given in http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html .
File input and output from the application has to be taken care of programatically (java.io stuff). Fine if you've only one input and output. But if you have several input files and hundreds of output files, where does this leave you. It would be much easier if you could pass a string command to the shell directly as if you typed it in the command line yoursel!

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sqlplusw.exe user/password@database @script3.sql
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I have a web-template built with BEx web application designer which also contains textboxes. This text should be stored by calling a webservice (standard BI-documents are not an option).
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Hello, can someone help me please
I am trying to process xml idocs into SAP on a Windows 2008 server. I have written a vbs script to process the file and am trying to call STARTRFC.EXE from within the vbs script. However I keep getting an error that it cannot open the file. The code is shown below. I have changed the server name and gateway and user/passwd for security. I'm passing the filename as a variable (str_expfile) but it does not seem to be able to extract the actual file name from the variable. I know from past experience that you can pass it variables if its running on a unix box and in a shell. But for some reason it not decipering the variable name in the vbs script
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ERROR file opened at 20110510 134219 GMT Daylight Time, SAP-REL 700,0,278 RFC-VER 3 1200864 MT-SL
T:2584 Error in program 'startrfc': ======> Error at OPEN 'str_expfile' (check file)
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Hi Markus
Unfortunately I can't do that because I need it to process hundreds of files one after another and I would have to hard code the file path each time. That's why I need it automated.
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Steve

How to call WebDynpro application from an external application

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Hi !
I'm trying to run a Java application from within a servlet with Tomcat 4. I'm using the Runtime.getRuntime ().exec () method. So the application is run in a different JVM as a subprocess of the servlet. I use ObjectInputStream and ObjectOutputStream and a serializable object to enable communication between the servlet and the application.
I tested the application and the serializable object with another Java application that works as the caller and it works fine. However, replacing the caller application with the servlet I get a StreamCorruptedException. The structure of the caller application and the servlet is the same.
My questions are:
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- What is the cause of the StreamCorruptedException ? How do I get it with the servlet and not with the application ?
- Should I use an environment with the call to Runtime.getRuntime ().exec () ? How do I use it ?
- Is the called application forced to run in my servlet's context ?
- Is there a better way to do this ?
Thanks to all

Here's my code:
1. The serializable object:
// Object Obj
import java.io.*;
public class Obj implements Serializable
public int n;
public Obj ()
n = 0;
public Obj (int n)
this.n = n;
public String toString ()
return getClass ().getName () + " -> (n = " + n + ")";
2. The application Sub (subprogram)
// Application Sub
import java.io.*;
public class Sub
private static File f;
private static FileWriter fw;
public static void main (String [] args)
throws IOException, InterruptedException, ClassNotFoundException
ObjectInputStream ois;
ObjectOutputStream oos;
Obj obj;
ois = new ObjectInputStream (System.in);
obj = (Obj) ois.readObject ();
f = new File ("Sub.txt");
fw = new FileWriter (f);
fw.write (obj.toString ());
fw.close ();
oos = new ObjectOutputStream (System.out);
oos.writeObject (obj);
ois.close ();
oos.close ();
3. The application AMain (caller application)
// Application AMain
import java.io.*;
class AMain
private static File f;
private static FileWriter fw;
public static void main (String [] args)
throws IOException, ClassNotFoundException
Runtime r;
Process p;
ObjectInputStream ois;
ObjectOutputStream oos;
Obj obj, obj2;
r = Runtime.getRuntime ();
p = r.exec ("java Sub");
oos = new ObjectOutputStream (p.getOutputStream ());
obj = new Obj (5);
oos.writeObject (obj);
oos.flush ();
B.comunica (obj);
System.out.println ("AMain sends to Sub: " + obj.toString ());
try
p.waitFor ();
catch (InterruptedException e)
System.out.println ("Subprogram was interrupted");
System.out.println (e.toString ());
ois = new ObjectInputStream (p.getInputStream ());
System.out.print ("Sub sends to AMain: ");
obj2 = (Obj) ois.readObject ();
System.out.println (" " + obj2.toString ());
oos.close ();
ois.close ();
p.destroy ();
4. The servlet SMain (the calling servlet)
// Servlet SMain
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
import java.io.*;
import java.util.*;
public class SMain extends HttpServlet
public void doPost (HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException
Runtime r;
Process p;
ObjectInputStream ois;
ObjectOutputStream oos;
Obj obj, obj2;
int state, i;
res.setContentType ("text/html");
ServletOutputStream out = res.getOutputStream ();
out.println ("<html>");
out.println ("<head><title>Sub</title></head>");
out.println ("<body>");
out.println ("Invoking subprogram...");
out.println (" ");
try
r = Runtime.getRuntime();
p = r.exec ("java -cp .;c:\\Programs\\Apache~1.0\\webapps\\SMain\\WEB-INF\\classes Sub");
out.println ("...invoked ");
oos = new ObjectOutputStream (p.getOutputStream ());
obj = new Obj (5);
oos.writeObject (obj);
oos.flush ();
out.println (" SMain sends to Sub: " + obj.toString () + " ");
try
p.waitFor ();
catch (InterruptedException e)
out.println (" Subprogram was interrupted ");
out.println (" " + e.toString () + " ");
state = p.exitValue ();
out.println (" Subprogram state: " + state + " ");
ois = new ObjectInputStream (p.getInputStream ());
out.print (" Sub sends to SMain: ");
obj2 = (Obj) ois.readObject ();
p.destroy ();
catch (SecurityException e)
out.println (" SecurityException ");
out.println (" " + e.toString () + " ");
catch (IOException e)
out.println (" IOException ");
out.println (" " + e.toString () + " ");
catch (Exception e)
out.println (" Exception ");
out.println (" " + e.toString () + " ");
out.println ("</body>");
out.println ("</html>");
So, as you can see, both application AMain and servlet SMain invoke application Sub and pass it the serializable object Obj. Oddly enough, application AMain works fine whereas servlet SMain throws a StreamCorruptedException exception.
johnpoole said:
�It's hard to guess what would cause the exception without seeing code, but the interaction between the processes would differ from that between two applications, because the servlet process is started with a different class loader. I'm not sure which one the jvm started by the call would use.�
How can I enforce that a System classloader be used in the call to Runtime.getRuntime ().exec () ? (I mean by System classloader a classloader equals to the one applications are launched from console).
johnpoole said
�Is there a reason why you aren't starting the second process manually and then connecting to it on a port?�
The idea is providing a Web interface for an application running in the server. The servlet is used to restrict access to this application but once access is granted (passing the servlet) the application should not be constrained.

Calling Java Application from another

How can i call a Java Application from another java App.
eg., If my Java application is called MyApp and i would like call another java application from within it.
One way could be by using "System". I would like to know if there is any other method and is portable.
Thanks in advance.

hi,
it works and not!
if you start an other class with a command like this the 2nd prog/class terminates too if you terminate the caller-class!
dear
oliver scorp

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Why doesn't the 'export -f FUNCTION' work as expected in the following:
#!/bin/bash
target="$1"
[[ -z "$target" ]] && echo "No target specified." && exit 1
work() {
bsdtar -xOf "$target" .PKGINFO | egrep -w 'pkgname|arch|pkgdesc|group|conflict|depend|replaces' | sed -e 's/pkgname/\npkgname/' >> /scratch/pkgs.log
export -f work
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It errors out when called:
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zsh:1: command not found: do_work
zsh:1: command not found: do_work
zsh:1: command not found: do_work
zsh:1: command not found: do_work
zsh:1: command not found: do_work
zsh:1: command not found: do_work
zsh:1: command not found: do_work
zsh:1: command not found: do_work
zsh:1: command not found: do_work
zsh:1: command not found: do_work
zsh:1: command not found: do_work

moetunes wrote:The command you are exporting is called work. The command it fails on is do_work
That was a copy/paste error based on me trying multiple scripts. Sorry about the confusion.
% ./test linux
zsh:1: command not found: work
zsh:1: command not found: work
falconindy wrote:
It's also the wrong solution to be exporting functions...
Yay for ineffective crossposting... https://bbs.archlinux.org/viewtopic.php?id=153461
Exporting functions is recommended in the parallel man page.
The command must be an executable, a script, a composed command, or a function. If it is a function you need to export -f the function first. An alias will, however, not work (see why http://www.perlmonks.org/index.pl?node_id=484296).
Also, how is this a cross post? The post you referenced is about parsing input, this one is about calling a function from within the parent script.
Awebb wrote:Why does zsh report a problem with a bash script?
No idea
Last edited by graysky (2012-11-24 14:35:15)

Calling a report from unix shell script

Hi,
I had to call a report from unix shell script.
May i know the procedure to accomplish this
Thanks in Advance
A.Gopal

First you should not include the whole path to your report in the call ...
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Calling external applications from within a script.

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