Develop Reference

aapt using Runtime.exec()

I want to run aapt using the Java runtime. My code is as follows:
String srcFile = "/home/jay/testing_FILES.apk";
String dsFile = "/home/jay/testing_FILES";
String firstCommand = ("/home/jay/android-sdk-linux/platform-tools/aapt " +
"package -u -f -F" + srcFile + dsFile);
try {
Runtime rt = Runtime.getRuntime();
Runtime.getRuntime().exec(firstCommand);
} catch (IOException e1) {
e1.printStackTrace();
}
This code doesn't give me an error, but it doesn't give me any results either. Any thoughts on how to fix this? Also this is meant to be portable code so if there is a way to do it without scripting that would be preferred.

You are trying to put the arguments in the same string as the command; that won't work here because there is no shell to parse them out.
You might want to try the form of exec() which takes a string array containing a command and it's arguments.

How to execute a interactive shell script using java Runtime?

I am wondering is there any way to execute following shell script, which waits for user input using java's Runtime class?
#!/bin/bash
echo "Please enter your name:"
read name
echo "Welcome $name"
I am using following java code to do this task but it just shows blank console.
public class TestShellScript {
public static void main(String[] args) {
File wd = new File("/mnt/client/");
System.out.println("Working Directory: " +wd);
Process proc = null;
try {
proc = Runtime.getRuntime().exec("sudo ./test.sh", null, wd);
} catch (Exception e) {
e.printStackTrace();
}
}
}
Thing is when I execute above program, I believed it will execute a shell script and that shell script will wait for user input, but it just prints current directory and then exits. Is there any way to do this or it is not possible at all in java?
Thanks in advance

The reason it prints the current dir and exits is because your java app exits. You need to add a (threaded) listener to the input and error streams of your created process, and you'll probably want to add a printStream to the process's output stream
example:
proc = Runtime.getRuntime().exec(cmds);
PrintStream pw = new PrintStream(proc.getOutputStream());
FetcherListener fl = new FetcherListener() {
#Override
public void fetchedMore(byte[] buf, int start, int end) {
textOut.println(new String(buf, start, end - start));
}
#Override
public void fetchedAll(byte[] buf) {
}
};
IOUtils.loadDataASync(proc.getInputStream(), fl);
IOUtils.loadDataASync(proc.getErrorStream(), fl);
String home = System.getProperty("user.home");
//System.out.println("home: " + home);
String profile = IOUtils.loadTextFile(new File(home + "/.profile"));
pw.println(profile);
pw.flush();
To run this, you will need to download my sourceforge project: http://tus.sourceforge.net/ but hopefully the code snippet is instructive enough that you can just adapt to J2SE and whatever else you are using.

If you use a Java ProcessBuilder you should be able to get the Input, Error and Output streams of the Process you create.
These streams can be used to get information coming out of the process (like prompts for input) but they can also be written to to put information into the process directly too. For instance:
InputStream stdout = process.getInputStream ();
BufferedReader reader = new BufferedReader (new InputStreamReader(stdout));
String line;
while(true){
line = reader.readLine();
//...
That'll get you the output from the process directly. I've not done it myself, but I'm pretty sure that process.getOutputStream() gives you something that can be written to directly to send input to the process.

The problem with running interactive programs, such as sudo, from Runtime.exec is that it attaches their stdin and stdout to pipes rather than the console device they need. You can make it work by redirecting the input and output to /dev/tty.
You can achieve the same behaviour using the new ProcessBuilder class, setting up the redirection using ProcessBuilder.Redirect.INHERIT.

Note sure at all you can send input to your script from Java. However I very strongly recommend to have a look at Commons Exec if you are to execute external scripts from Java:
Commons Exec homepage
Commons Exec API

How can I launch VI from within Java under commons-exec?

I would like to be able to launch VI from within my Java program and wait for the user to quit VI before proceeding. Here's the code snippet that I have currently:
...
String previewFileName="test.txt"; // the file to edit
CommandLine cmdLine = new CommandLine("/usr/bin/vi");
cmdLine.addArgument(previewFileName);
cmdLine.addArgument(">/dev/tty");
cmdLine.addArgument("</dev/tty");
Executor executor = new DefaultExecutor();
try
{
DefaultExecuteResultHandler resultHandler = new ResetProcessResultHandler(cmdLine);
executor.execute(cmdLine, resultHandler);
} catch (IOException e)
{
throw new Error("Cannot execute command: /usr/bin/vi " + previewFileName, e);
}
log.info("waiting...");
cmdLine.wait();
log.info("...done");
...
private class ResetProcessResultHandler extends DefaultExecuteResultHandler
{
private final CommandLine mCommandLine;
public ResetProcessResultHandler(CommandLine pCommandLine)
{
mCommandLine = pCommandLine;
}
public void onProcessComplete(int exitValue)
{
log.info("Command complete rc(" + exitValue + ")");
if (exitValue != 0)
{
throw new RuntimeException("VI command error [rc=" + exitValue + "] " );
}
mCommandLine.notify();
}
public void onProcessFailed(ExecuteException e)
{
if (e.getExitValue() != 0)
{
log.error("launch VI error " + e.toString());
throw new RuntimeException("VI command failed [" + e.getCause() + "] ");
}
else
{
log.info("VI complete rc(" + e.getExitValue() + ")");
}
mCommandLine.notify();
}
}
I receive output:
Vim: output is not to a terminal
Vim: input is not from a terminal
But then I see the screen painted as if VI had started; and VI doesn't read characters I type.
So ... redirecting from /dev/tty isn't doing the trick.
Someone must have done this before - help!
Thanks,
Mark

However since Java 1.7 you can use the next example to transparently redirect and have full console functionality
System.out.println("STARTING VI");
ProcessBuilder processBuilder = new ProcessBuilder("/usr/bin/vi");
processBuilder.redirectOutput(ProcessBuilder.Redirect.INHERIT);
processBuilder.redirectError(ProcessBuilder.Redirect.INHERIT);
processBuilder.redirectInput(ProcessBuilder.Redirect.INHERIT);
Process p = processBuilder.start();
// wait for termination.
p.waitFor();
System.out.println("Exiting VI");
This will allow you to open VI transparently for JVM 1.7+.

When Java runs a program via Runtime.exec() (and this is what commons-exec does in the end), it connects the program's input, output and error streams to your Java app as input/output streams. Such a stream is certainly not a terminal, you can't for example move the text cursor in it (since it doesn't have any), change text colors, or detect if Shift key is pressed (since it's just a stream of bytes and not a physical keyborad). So, an interactive app like vi can't really function under such conditions like in a terminal.
By the way, I'm not sure if the command line args you supply are parsed by the shell or passed directly to the program. In the latter case your redirection to /dev/tty couldn't possibly work even if there was a way for Java to somehow allow the program to replace Java's connected streams with something else.
As an aside, it seems a bit strange why you would like to run vi from inside a Java program.
So I guess the best solution is to execute a terminal emulator like konsole or gnome-terminal or xterm and let it run vi by passing corresponding argument on its command line (e.g. konsole -e vi). In this case the terminal's window should pop up and vi could function inside it. Of course, it won't work if you're on a headless server, but then running vi can't be useful anyway.

I'm not sure how to do it with commons-exec,
But standard Java should be something along the lines of...
String[] command = {"/usr/bin/vi", "test.txt"};
Process vimProcess = Runtime.getRuntime().exec(command);
vimProcess.waitFor();
This will cause the current thread to wait for the process to complete. You can also use
vimProcess.getInputStream(), getOutputStream() and getErrorStream() to redirect those to log files or wherever you want it to go.
See here for more details.
http://docs.oracle.com/javase/6/docs/api/java/lang/Runtime.html
Hopefully this helps.

How to realize "mklink /H" (hardlinking) in Java?

i want to create a hardlink from a file "C:\xxx.log" to "C:\mklink\xxx.log" .
In cmd it works of course, but i want to write a software for this usecase.
So have to locate the existing file
Then make a hardlink
Then delete the old file
I started to implement but, i just know how to create a file. On google i found nothing about mklink \H for Java.
public void createFile() {
boolean flag = false;
// create File object
File stockFile = new File("c://mklink/test.txt");
try {
flag = stockFile.createNewFile();
} catch (IOException ioe) {
System.out.println("Error while Creating File in Java" + ioe);
}
System.out.println("stock file" + stockFile.getPath() + " created ");
}

There are 3 ways to create a hard link in JAVA.
JAVA 1.7 Supports hardlinks.
http://docs.oracle.com/javase/tutorial/essential/io/links.html#hardLink
JNA, The JNA allows you to make native system calls.
https://github.com/twall/jna
JNI, you could use C++ to create a hardlink and then call it through JAVA.
Hope this helps.

Link (soft or hard) is a OS feature that is not exposed to standard java API. I'd suggest you to run command mklink /h from java using Runitme.exec() or ProcessBuilder.
Or alternatively try to find 3rd party API that wraps this. Also check what's new in Java 7. Unfortunately I am not familiar with it but I know that they added rich file system API.

For posterity, I use the following method to create links on *nix/OSX or Windows. On windows mklink /j creates a "junction" which seems to be similar to a symlink.
protected void makeLink(File existingFile, File linkFile) throws IOException {
Process process;
String unixLnPath = "/bin/ln";
if (new File(unixLnPath).canExecute()) {
process =
Runtime.getRuntime().exec(
new String[] { unixLnPath, "-s", existingFile.getPath(), linkFile.getPath() });
} else {
process =
Runtime.getRuntime().exec(
new String[] { "cmd", "/c", "mklink", "/j", linkFile.getPath(), existingFile.getPath() });
}
int errorCode;
try {
errorCode = process.waitFor();
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
throw new IOException("Link operation was interrupted", e);
}
if (errorCode != 0) {
logAndThrow("Could not create symlink from " + linkFile + " to " + existingFile, null);
}
}

Outputting result of "dir" to console in Java

I want to output the result of the "dir" command to the java console. I have already looked on Google and here, but none of the examples work for me, thus making me rite this post.
My code is as follows:
try
{
System.out.println("Thread started..");
String line = "";
String cmd = "dir";
Process child = Runtime.getRuntime().exec(cmd);
//Read output
BufferedReader dis = new BufferedReader( new InputStreamReader(child.getInputStream() ));
while ((line = dis.readLine()) != null)
{
System.out.println("Line: " + line);
}
dis.close();
}catch (IOException e){
}
What am I doing wrong?
Any help would be very nice.
Thanks in advance,
Darryl

You cannot run "dir" as a process, you need to change it to String cmd = "cmd dir";.
You don't handle the exception at all. adding the line e.printStackTrace()); in the catch block would tell you what I wrote in (1). Never ignore exceptions!
You don't handle error stream. This might cause your program to hang, handle error stream and read from both streams (error and input) in parallel using different streams.

The best way is to use commons exec http://commons.apache.org/exec/
This has things that catch quirks that can really drive you up the wall, such as the whole process blocking if you didn't clear its output stream, escaping quotes in commands, etc.
Here is a method that will run the del command in windows successfully. Note the use of cmd since del is not a standalone executable:
private void deleteWithCmd(File toDelete) throws IOException {
CommandLine cmdLine = new CommandLine("cmd.exe");
cmdLine.addArgument("/C");
cmdLine.addArgument("del");
cmdLine.addArgument(toDelete.getAbsolutePath());
DefaultExecutor executor = new DefaultExecutor();
int exitValue = executor.execute(cmdLine);
}

a) What is the java console?
b) You should use javas File.listFiles () instead of Runtime.exec, which isn't portable, and makes Name splitting neccessary - a hard thing, for filenames which contain spaces, blanks, newlines and so on.
c) Whats wrong with your code?
d) Why don't you do anything in the case of Exception?

Here is a more thorough example that accounts for OS versions and error conditions ( as stated by MByD above)
http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html?page=4
Remember that using "exec" means that your application is no longer cross-platform and loses one of the main advantages of Java.
A better approach is to use java.io package.
http://download.oracle.com/javase/tutorial/essential/io/dirs.html

You can also do something like that in java 6 :
import java.io.File;
import java.io.FilenameFilter;
import java.io.IOException;
public class ListFilesFromRegExp {
public static void main(String[] args) throws IOException {
File dir = new File("files/");
File[] files = dir.listFiles(new FilenameFilter() {
public boolean accept(File dir, String name) {
return name.matches("File[0-9].c");
}
});
for (int i = 0; i < files.length; i++) {
System.out.println(files[i].getAbsolutePath());
}
}
}