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();
}
}
}
Related
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.
I do have some serious troubles understanding the console in java. I am running Eclipse, and I wanted to write a small program which prompts a few text messages to the console and receives a few strings as input arguments from it. Problem is: When I run my program, it opens the command line window properly, but my outputs are only printed on the Eclipse-Console.
In some way, I do understand why this is the case. The Command Line Windows expects commands, and not just some kind of a string or something. But how do i manage to output my Strings into the Command Line Window and read Strings from it, and not just commands.
Or am I doing it the wrong way? Do I have to open another "Console" where all my messages will be prompted and from which i can read strings a user wrote?
This is the code i use to open a command line window on start:
public static void main(String args[]) throws Exception {
Process process = new ProcessBuilder(new String[] { "cmd", "/C",
"start", "cmd" }).start();
System.out.println(process.waitFor());
Edit: I did still not manage to get this to working. Somehow, when I compiled the program, and I run it, it properly opens a command window, but no messages are posted there. Seems like "System.out.println("xxx") does not have any effect on this window.
There's no "console" specified by your program, but an stdin, stdout and stderr for input, output and error output. When you run your program from windows, these streams are bound to a command window, and if you run it in eclipse, they will be associated to the eclipse console. To give a more obscure example, ff you were running it through ssh, the streams would be associated to ssh, and ssh associated to your command window, and so on.
So, you're not doing anything wrong, you just need to run the program from the command line if you want stdout and stdin to come from that command window.
How do you open a command window, by the way?
You might want to read through this page:
http://pages.cs.wisc.edu/~hasti/cs368/JavaTutorial/NOTES/JavaIO_Scanner.html
Basically what you need to is create the input stream, tell the user to input something, and then get the input. E.g.
private static Scanner newScanner = new Scanner(System.in);
public static void main(String[] args) {
System.out.println("Put your input here: ");
String inputValue = newScanner.nextLine();
System.out.println(inputValue);
}
Just remember to import the scanner library!
I am creating a program that requires a input/output system, since this program doesn't have GUI, and I am launching it from a JAR file, I was wondering how I can create the input/output system.
Im starting to learn about JAR files, and normally I just run my finished program via a batch script. So how can I get this terminal like input/output system from a JAR? #beginner
As there is no UI, you should run your program from Console (terminal) to use standard input/output. If you are in Window use (.bat) or if you are in linux use shell script(.sh) to call your jar
I don't know if this is what you are asking for, but try this:
java -jar inout.jar
HELLO
gwag
Your input: gwag
faefa
Your input: faefa
feafa
Your input: feafa
faef
Your input: faef
public class Test {
public static void main(String[] args) throws InterruptedException {
System.out.println("HELLO");
Scanner scanner = new Scanner(System.in);
while(scanner.hasNext()) {
System.out.println("Your input: " + scanner.next());
}
}
}
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).