I want to read all output from a running application in my own java application. Currently I have 2 screens, in the first the output application prints permanently new informations and the second with the java application. Unfortunately it is not possible to run both applications in one screen. My idea was to pipe all output to the java application screen to read it in there, but I do it wrong or it doesn't work.
My (test) server looks like this:
public class Main {
public static void main(String[] args) throws InterruptedException {
while (true) {
Scanner scanner = new Scanner(System.in);
String output = scanner.next();
System.out.print("JAVA " + output);
}
}
}
and my linux start file like this:
#!/bin/bash
cd ../../raspberry-remote/
screen -dmS smarthome_javaserver #here runns the java application
screen -dmS smarthome_receive | smarthome_javaserver #send the output to the java screen
#start java app
screen -S smarthome_javaserver -p 0 -X stuff "java -jar ServerReceiver.jar^M"
#start receive tool
screen -S smarthome_receive -p 0 -X stuff "pilight-daemon -D^M"
screen -S smarthome_receive -p 0 -X stuff "pilight-daemon -D^M"
echo "started receiver"
Anyone knows how to realize this, or is there a way to let them run in one screen? Thanks for help.
I'm not quite sure about this but I can point you in the right direction I think. First you would have to start the application which you could do using "ProcessBuilder" and after creating the process you would need a input stream reader to read the output.
In code it would look something like this:
ProcessBuilder b = new ProcessBuilder("myapp");
Process app = builder.start();
//app is running now read its output
InputStreamReader stream = new InputStreamReader(app.getInputStream());
You can now read in the output of app I would recommand using a BufferedReader which has an easier interface. I always read from a stream like this:
BufferedReader br = new BufferedReader(stream))
for(String line; (line = br.readLine()) != null; )
{
ProcessLine(line);
}
I hope this helps you out a little.
Related
I am making simple console app. My main loop looks like this.
var s = new Scanner(System.in);
while (appShouldRun) {
var action = s.nextLine();
// proccess action
}
It works fine when I run app with empty stdin.
java -jar app.jar
But I want to have some prepared scenarios in file. Run them and then wait for next user input.
Expected behaviour:
java -jar app.jar < scenario.txt
output of commands from file
| <- cursor, waiting for user input
// scenario.txt
cmd1
cmd2
cmd3
.
.
.
Problem is that when I run program with something od std in, it process commands correctly, but then it throws
java.util.NoSuchElementException: No line found
I think it's becouse stdin is closed after all lines from file is processed.
Am I wrong?
How to fix the code to get expected behaviour?
Thanks
When you redirect standard input with <, it is connected to the input file, and not connected at all to the console.
If you want your program to receive input on the console, then you can't redirect stdin. You should take the filename as a command-line argument instead. Open it, read it, close it, and then process stdin.
OR, if you really want to, and you're on a unix/linux/macOS system, you can run it like this, using the cat command to concatenate standard input to something else:
cat scenario.txt - | java -jar app.jar
I have tried do change as little code as possible. This reads the whole file like you wanted and ends without Exception
public class Main {
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
boolean appShouldRun = true;
while (appShouldRun) {
String action = s.nextLine();
System.out.println("got: " + action);
appShouldRun = s.hasNext();
}
}
}
I am using the process class to run this command
/sdcard/file1.mpg /sdcar/file2.mpg > /sdcard/out.mpg
Here is how I am trying to do it:
Process processx = Runtime.getRuntime().exec(new String[] {"cat","/sdcard/file1.mpg /sdcard/file2.mpg > /sdcard/out.mpg" });
BufferedReader in = new BufferedReader(new InputStreamReader(processx.getInputStream()));
String line = null;
while ((line = in.readLine()) != null) {
System.out.println(line);
}
// Waits for the command to finish.
processx.waitFor();
The command works from terminal but not when I try the above, can anyone see why?
Redirection (>) is not the OS feature. This is a feature of shell. To make it working from java you have to run something like the following:
/bin/sh yourcommand > yourfile
i.e. in your case:
/bin/sh cat /sdcard/file1.mpg /sdcard/file2.mpg > /sdcard/out.mpg
BUT could you please explain me why are you doeing this? Do you understand that this command is exact equivalent of cp /sdcard/file1.mpg /sdcard/file2.mpg /sdcard/out.mpg that can be coded in pure java without running any command line? Unless you have special reasons go on it! Write pure java code when it is possible. It is easier to debug, support and maintain.
There's absolutely no reason to use 'cat' to do this. It's not a supported or encouraged mechanism on Android, and there's no reason to launch a new executable to do what you can easily do in java code, by reading in one file and writing it out to the other.
For the record, you are trying to do a shell redirection, and that will not work since you are not executing a shell.
im using this small code to execute "cat" command and most of shell commands:
String[] cmdline = { "sh", "-c", "cat /sdcard/file1 >> /sdcard/file2" };
try {
Runtime.getRuntime().exec(cmdline);
} catch (Exception s) {
finishAffinity();
}
I am facing a weird issue with executing a system command from JAVA code.
Actually i want to get the Mac OSX system information from my JAVA App.
For that im using
Runtime.getRuntime().exec("system_profiler -detailLevel full");
This is working fine.If i print the output,it is cool.
But i want to write this information to a plist file for future use.For that im using the -xml argument of system_profiler.like,
String cmd = "system_profiler -detailLevel full -xml > "+System.getProperty( "user.home" )+"/sysinfo.plist";
Process p = Runtime.getRuntime().exec(cmd);
Basically this should create a plist file in the current users home directory.
But this seems to be not writing anything to file.
Am i missing something here ?
My Java is more than rusty, so please be gentle. ;-)
Runtime.exec() does not automatically use the shell to execute the command you passed, so the IO redirection is not doing anything.
If you just use:
"/bin/sh -c system_profiler -detailLevel full > path/file.plist"
Then the string will be tokenized into:
{ "/bin/sh", "-c", "system_profiler", "-detailLevel", "full", ">", "path/file.plist" }
Which also wouldn't work, because -c only expects a single argument.
Try this instead:
String[] cmd = { "/bin/sh", "-c", "system_profiler -detailLevel full > path/file.plist" };
Process p = Runtime.getRuntime.exec(cmd);
Of course, you could also just read the output of your Process instance using Process.getInputStream() and write that into the file you want; thus skip the shell, IO redirection, etc. altogether.
Christian.K is absolutely correct. Here is a complete example:
public class Hello {
static public void main (String[] args) {
try {
String[] cmds = {
"/bin/sh", "-c", "ls -l *.java | tee tmp.out"};
Process p = Runtime.getRuntime().exec (cmds);
p.waitFor ();
System.out.println ("Done.");
}
catch (Exception e) {
System.out.println ("Err: " + e.getMessage());
}
}
}
If you weren't using a pipe (|) or redirect (>), then you'd be OK with String cmd = "ls -l *.java", as in your original command.
If you actually wanted to see any of the output in your Java console window, then you'd ALSO need to call Process.getInputStream().
Here's a good link:
Running system commands in Java applications
My aim with this project was to have a remote command prompt feel with Java. Using TCP/IP sockets, I was aiming to run a command prompt process on one computer, and virtually transmit all control to the other side. I immediately stumbled over Runtime.getRuntime().exec() and Process objects, etc. I've solved my problem about halfway. With my remote command prompt, I can run a single command, gather the output, and send it back to the other side. The problem is, I can only seem to run one command per command prompt instance. This won't do (with situations where I need to change directory and THEN run a command, etc). I've stripped all socket/networking programming from this situation to show you (and to create an easier testing environment for me).
import java.io.*;
public class testingProgram {
public static void main(String[] args) {
Runtime rt = Runtime.getRuntime();
StringBuilder inputMessage = new StringBuilder();
String resultData;
try {
Process pr = rt.exec("cmd.exe /c net user");
BufferedReader processInput = new BufferedReader(new InputStreamReader(pr.getInputStream()));
BufferedReader errorProcessInput = new BufferedReader(new InputStreamReader(pr.getErrorStream()));
PrintWriter processOut = new PrintWriter(pr.getOutputStream());
while( (resultData = processInput.readLine()) != null ) {
inputMessage.append(resultData + "\n");
}
resultData = inputMessage.toString();
System.out.print(resultData);
} catch(IOException e) {
} //catch(InterruptedException e) {
//}
}
}
I have a lot more, but this is where my problem is. I can customize the command "net user" with a simple variable and message from the socketstream, so that's not my problem. My problem is that I need to create an ongoing command prompt instance, retaining all redirections of the input/output. Basically, I would like to be able to send another command AFTER "net user".
I have gathered and redirected the output stream. I want to be able to do something like:
processOut.write("net user");
I want to be able to use this, have the command prompt run the command, and retain the output (whether it be from the errorStream OR the inputStream).
I just need some more direction on how to go about doing this.
You should look into multi threading. What you basically want is a thread which keeps running and maintaining the rt.
Like this:
String commandLine;
while ((commandLine = System.in.readline()) != 'q') {
Process pc = rt.exec(commandLine);
}
For further reference on multithreading:
http://download.oracle.com/javase/tutorial/essential/concurrency/procthread.html
You problem is that your program terminates after one call.
cheers
You're telling the command interpreter to terminate. Remove the /C after cmd.exe.
cmd /?
Starts a new instance of the Windows command interpreter
CMD [/A | /U] [/Q] [/D] [/E:ON | /E:OFF] [/F:ON | /F:OFF] [/V:ON | /V:OFF]
[[/S] [/C | /K] string]
/C Carries out the command specified by string and then terminates
/K Carries out the command specified by string but remains
...
I want to exceute a simple command which works from the shell but doesn't work from Java.
This is the command I want to execute, which works fine:
soffice -headless "-accept=socket,host=localhost,port=8100;urp;"
This is the code I am excecuting from Java trying to run this command:
String[] commands = new String[] {"soffice","-headless","\"-accept=socket,host=localhost,port=8100;urp;\""};
Process process = Runtime.getRuntime().exec(commands)
int code = process.waitFor();
if(code == 0)
System.out.println("Commands executed successfully");
When I run this program I get "Commands executed successfully".
However the process is not running when the program finishes.
Is it possible that the JVM kills the program after it has run?
Why doesn't this work?
I'm not sure if I'm not mistaken, but as far as I see you're generating the commands but never passing them to the "execute" method... you're executing "".
Try using Runtime.getRuntime().exec(commands) =)
I would like to say how I solved this.
I created a sh script that basically run the command of soffice for me.
Then from Java I just run the script, and it works fine, like this:
public void startSOfficeService() throws InterruptedException, IOException {
//First we need to check if the soffice process is running
String commands = "pgrep soffice";
Process process = Runtime.getRuntime().exec(commands);
//Need to wait for this command to execute
int code = process.waitFor();
//If we get anything back from readLine, then we know the process is running
BufferedReader in = new BufferedReader(new InputStreamReader(process.getInputStream()));
if (in.readLine() == null) {
//Nothing back, then we should execute the process
process = Runtime.getRuntime().exec("/etc/init.d/soffice.sh");
code = process.waitFor();
log.debug("soffice script started");
} else {
log.debug("soffice script is already running");
}
in.close();
}
I also kill the soffice process by calling this method:
public void killSOfficeProcess() throws IOException {
if (System.getProperty("os.name").matches(("(?i).*Linux.*"))) {
Runtime.getRuntime().exec("pkill soffice");
}
}
Note that this only works in Linux.
I believe you aren't handling quoting correctly. The original sh command line includes double quotes to prevent the shell interpreting the semicolons. The shell strips them off before the soffice process sees them.
In your Java code the shell will never see the arguments, so the extra double quotes (escaped with backslashes) are not needed - and they are probably confusing soffice.
Here's the code with the extra quotes stripped out (and a semicolon thrown in)
String[] commands = new String[] {"soffice","-headless","-accept=socket,host=localhost,port=8100;urp;"};
Process process = Runtime.getRuntime().exec(commands);
int code = process.waitFor();
if(code == 0)
System.out.println("Commands executed successfully");
(Disclaimer: I don't know Java, and I haven't tested this!)
"/Applications/OpenOffice.org\ 2.4.app/Contents/MacOS/soffice.bin -headless -nofirststartwizard -accept='socket,host=localhost,port=8100;urp;StartOffice.Service'"
or simply escaping the quotes will work as well. We feed a command like this to an ant script that ultimately ends up in an exec call like you have above. I would also recommend restarting the process every 500 or so conversions because OOO does not properly free memory (depending on what version you are running).