I want to run different commands which can be executed on my command prompt or terminal through Java.
I did search few place but did not get appropriate reply.
I want to run a compiler which is set in the environment as VISAGE_HOME as well as run GRADLE so as to do all my build tasks.
I want to invoke all these commands from within Java Program.
Since it is a swing application I would like to invoke these commands on click of button or some other events.
My Problem is that I am not able to program this :( .
Neither do I know an API which would do this. I went through some sample codes but most of them have same kind of example codes of executing the shell commands or command prompt commands. None showed me to do the above stuff.
Have a look at ProcessBuilder. The Process object it returns has a waitFor method so you can wait for the process to finish. Then you can start your next process.
For example
Process p = new ProcessBuilder("runYourCommand").start();
InputStream in = process.getInputStream();
InputStreamReader inr = new InputStreamReader(in);
BufferedReader br = new BufferedReader(inr);
String inputLine;
while ((inputLine = br.readLine()) != null) {
System.out.println(inputLine);
}
p.waitFor();
Another interesting method on ProcessBuilder is environment(). This will return the environment variables that you can access. From the API docs
Map<String, String> env = pb.environment();
env.put("VAR1", "myValue");
Something like this:
String cmd = "gedit";
Runtime run = Runtime.getRuntime();
Process pr = run.exec(cmd);
Firstly, ProcessBuilder is your friend...
You could have a look at;
Getting started with Java’s ProcessBuilder (Linux focus)
Using ProcessBuilder to Make System Calls
Run processbuilder and get in and output
ProcessBuilder and how redirecting input and output from operating system's processes
Executing Operating System Commands from Java
Secondly, You will need to use System.getenv to find the value of the specified environment variable and substitute it yourself.
nb: Thanks to Guillaume Polet for pointing out that the Process will automatically include the path environment variable to find commands.
Also, remember, DO NOT EXECUTE ANY BLOCKING PROCESS ON THE EDT.
Executing external commands are inherently blocking actions, while not explicitly, taking into account needing to consume the output of the process or wanting to know about the processes termination, these would require you to perform some kind of blocking action. Don't do this on the EDT. It will cause you program to appear as if it's hung.
You can use the Runtime.exec methods to run commands from within Java. The system enviroment variables are normally not visible from within the jvm. You could use a launcher, that submits these system enviroment properties as jvm properties to your java application.
According to http://javarevisited.blogspot.de/2011/02/how-to-execute-native-shell-commands.html implementing the following into your code after including "java.lang.Runtime" should perfectly work:
try {
Process process = Runtime.getRuntime().exec("Command to be executed");
} catch (Exception e) {
e.printStackTrace(System.err);
}
Related
In Java, I start one new Process using Runtime.exec(), and this process in turn spawns several child processes.
I want to be able to kill all the processes, and have previously been trying process.destroy() and process.destroyForcibly() - but the docs say that destroyForcibly() just calls destroy() in the default implementation and destroy() may not kill all subprocesses (I've tried and it clearly doesn't kill the child processes).
I'm now trying a different approach, looking up the PID of the parent process using the method suggested here and then calling ps repeatedly to traverse the PIDs of child processes, then killing them all using kill. (It only needs to run on Linux).
I've managed the first bit - looking up the PID, and am trying the following command to call ps to get the child PIDs:
String command = "/bin/ps --ppid " + pid;
Process process = new ProcessBuilder(command).start();
process.waitFor();
Unfortunately the 2nd line above is throwing an IOException, with the following message: java.io.IOException: Cannot run program "/bin/ps --ppid 21886": error=2, No such file or directory
The command runs fine if I paste it straight into the terminal on Ubuntu 16.04.
Any ideas would be very much appreciated.
Thanks
Calling the command you wish to run this way is always destined to fail.
Since Process does not effectively run a shell session, the command is basically handed over to the underlying OS to run. This means that it'll fail, since the path to t he program to be executed (in this case ps), is not the full one hence the error you're getting.
Also, testing whether your command works using a terminal is not correct. Using a terminal contains the notion of performing an action with an active logged in user with a correct path etc etc. All the above are not the case though when running a command through Process as these are not taken into consideration.
Furthermore, you also need to account for cases where the actual java application could be running under a different user, with a different set of permissions, paths etc.
In order for your to fix this, you can simply do either of the following:
1) Invoke your ps command using the full path to it (still not sure if it would work)
2) Change the way your create the Process object into something like: p = new ProcessBuilder("bash", "-c", command).start();
The second, will effectively run a bash session, passing in the ps command as an argument thus obtaining the desired result.
http://commons.apache.org/proper/commons-exec/tutorial.html
```
String line = "AcroRd32.exe /p /h " + file.getAbsolutePath();
CommandLine cmdLine = CommandLine.parse(line);
DefaultExecutor executor = new DefaultExecutor();
int exitValue = executor.execute(cmdLine);
```
I'm running a jar file from another jar like here somebody answers but waiting for the process.
Process proc = Runtime.getRuntime().exec("java -jar A.jar" + stringParams);
try {
proc.waitFor();
} catch (InterruptedException e) {
e.printStackTrace();
}
InputStream in = proc.getInputStream();
InputStream err = proc.getErrorStream();
My problem comes when i have no feedback on the status of the program that is called, but i don't want my program continues beyond those lines. I would need the standard and error outputs but the results are shown when the execution is over. Is there any way of executing and getting those streams while the jar is still running?
Buffered/unbuffered
It seems like an issue with buffered output.
Executed process (in this case java -jar <path>) buffers output and writes it only when it's done (in big chunks, we don't like that!)
So one way to go is execute process through unbuffering (very hacky tools):
unbuffered <command>
stdbuf -i0 -o0 -e0 <command>
use terminal emulation
Hacking
stdbuf is part of GNU tools.
https://www.gnu.org/software/coreutils/manual/html_node/stdbuf-invocation.html
unbuffered is part of expect package.
https://wiki.tcl.tk/3548
The key thing is making the program thinking that it's in interactive mode (like you are launching it from console).
The first two options are very hacky and do not work in all cases (idk if java command works with them?)
Emulation
The third option is most promising.
We launch a program (terminal emulator) that emulates interactive terminal making program think it's working in real active session!
Pty4j
You might use pty4j too:
From there: https://github.com/traff/pty4j
// The command to run in a PTY...
String[] cmd = { "java", "-jar", "path_to_jar" };
// The initial environment to pass to the PTY child process...
String[] env = { "TERM=xterm" };
PtyProcess pty = PtyProcess.exec(cmd, env);
OutputStream os = pty.getOutputStream();
InputStream is = pty.getInputStream();
// ... work with the streams ...
// wait until the PTY child process terminates...
int result = pty.waitFor();
// free up resources.
pty.close();
Zt-exec
Maybe it's worth trying zt-exec?
I have no idea how it executes commands.
But it may be it (I didn't test that).
Using https://github.com/zeroturnaround/zt-exec
new ProcessExecutor().command("java", "-jar path_to_jar")
.redirectOutput(new LogOutputStream() {
#Override
protected void processLine(String line) {
...
}
})
.execute();
That should work, but I didn't test that.
In general, there are no ways to nicely resolve your problem.
Depending on what platforms you want to target consider using unbuffered, stdbuff or the (slowest) terminal emulation...
Please let me know if that helps and good luck! :)
This has got to be one of the strangest things I have ever observed. Consider the following Java program:
import java.io.IOException;
public class StrangeError {
public static void main(String[] args) {
try {
Process process = new ProcessBuilder(
"cmd",
"/c",
"\"C:\\Program Files (x86)\\Microsoft Visual Studio 14.0\\VC\\vcvarsall.bat\" amd64 && set"
).start();
process.waitFor();
} catch (IOException|InterruptedException e) {
System.out.println(e.getMessage());
}
}
}
I compiled it with javac StrangeError.java, copied it to my server running Windows Server 2012 R2, and ran it with java StrangeError.
Here's where things start to get weird. The program hangs, waiting for the process it spawned to finish. This is not the expected behavior, since the vcvarsall.bat script should complete immediately as well as set.
So I started playing around and discovered the following:
Removing set causes vcvarsall.bat to terminate
Removing vcvarsall.bat causes set to terminate
Replacing && with || causes everything to terminate correctly
Copying vcvarsall.bat to a location on the desktop and changing the path causes everything to terminate correctly
A nearly equivalent program works fine in Go using the same commands
I get this output if I run everything in WinDbg and interrupt the process after it hangs
This does not appear to be reproducible with vcvarsall.bat from MSVC2013 but is also reproducible with MSVC2015 on Windows 10
What on earth is wrong with the original program? If I copy and paste the entire command (cmd /c "C:\...) into Start->Run, it immediately launches cmd and terminates, as expected.
Is this a bug with Java? Is this a bug with Windows?
Is this a bug with Java? Is this a bug with Windows?
It's a bug in your code. :-)
By default, a child process created using a ProcessBuilder object has output redirected to a pipe, the parent end of which can be obtained using Process.getInputStream() and which is not automatically drained if your code does not make use of it.
Since your code simply calls .waitFor without making any provision to drain the pipe, it will deadlock as soon as the pipe's buffer overflows. I believe the default buffer size is 4,096 bytes. On my machine, the output of the command you're running is 5,192 bytes, but this will vary depending on the original contents of the environment block. (From the sounds of it, the output length in your environment is borderline, only just above the limit, so that even small changes like changing the version of VS make a difference.)
One of the many possible solutions, depending on what you're actually trying to do, is to tell Java not to pipe the child's output:
import java.io.IOException;
public class StrangeError {
public static void main(String[] args) {
try {
ProcessBuilder processb = new ProcessBuilder(
"cmd",
"/c",
"\"C:\\Program Files (x86)\\Microsoft Visual Studio 14.0\\VC\\vcvarsall.bat\" amd64 && set"
);
processb.redirectOutput(ProcessBuilder.Redirect.INHERIT);
Process process = processb.start();
process.waitFor();
} catch (IOException|InterruptedException e) {
System.out.println(e.getMessage());
}
}
}
Not possible to read standard input and output error inside the same ProcessBuilder.
So you need to create two ProcessBuilder
Process process1 = new ProcessBuilder(
"cmd",
"/c",
"\"C:\\Program Files (x86)\\Microsoft Visual Studio 14.0\\VC\\vcvarsall.bat\",
"amd64");
Process process2 = new ProcessBuilder(
"cmd",
"/c",
"set");
process1.start();
if (process1.waitFor() == 0) {
process2.start();
if (process2.waitFor() == 0) {
// Successfull execution
}
}
And one thing : I don't think it is a good practice to do shell/batch launches with Java (or another language). Maybe you should use a script (shell, batch, python, perl...) to control standard input/output streams.
It's not the first time I have tried to execute a system command from Java; but this time it turns out to be very hard. I have a script that executes just fine from the terminal. It reads input from a file (input.txt), it processes it and exports the result in another file (ouput.txt). The whole thing lasts no more than 1sec. But, when I try to execute it from Java, it gets stuck and never finishes. This is my code:
Process p = new ProcessBuilder("./runCalculator.sh").start();
p.waitFor();
I have also tried with Runtime.getRuntime().exec("./runCalculator.sh") but all the same. I've read both the InputStream and the ErrorStream of the process. The error stream returns nothing but a message like "Starting Calculation..."
Any ideas?
You need to use the following code:
ProcessBuilder pb = new ProcessBuilder();
pb.command("bash", "-c", "./runCalculator.sh");
Process process = pb.start();
int retValue = process.waitFor();
You likely need to invoke the unix command interpreter/processor for this to work. Please see: When Runtime.exec() won't.
Try this:
Process p = new ProcessBuilder("sh ./runCalculator.sh").start();
Another, simplier solution is that you can open program by entering the name of the program (this assumes that program is installed) instead of creating script and calling it.
Note that the name of the program isn't always what you see in Gnome's menu, for example Gnome's calculator is "gnome-calculator". Regarding this facts, you can run calculator by the folowing line:
Process p = Runtime.getRuntime().exec("gnome-calculator");
In that case you don't have a need for any sh scripts (in your case runCalculator.sh).
I have written a java program named Automate.java, in which the another java program named newsmail will be executed.
The problem i face here is, Automate.java is in Desktop location(should be in desktop only always due to some requirements) and newsmail is in /home/Admin/GATE521/LN_RB this location.
What must be done before the below code, such that the command prompt automatically goes to the required folder and executes the program.
String command = "java newsmail";
Process child = Runtime.getRuntime().exec(command);
You can use this exec() :
Process child = Runtime.getRuntime().exec(command, null, new File("/home/Admin/GATE521/LN_RB"));
Resources :
javadoc - Runtime.exec()
Use the new ProcessBuilder class, instead of Runtime.exec().
ProcessBuilder pb = new ProcessBuilder("java", "newsmail");
pb.directory("/home/Admin/GATE521/LN_RB");
pb.start();
You can even look at pb.environment() to change environment variables if necessary.