I have a function in java which is being executet on my raspberry pi and should send a signal to toggle the targeted sockets state to on / off.
Thats my current function:
public static void rcswitch(int housecode,int unitcode, int onoff) throws InterruptedException, IOException {
String housestring = Integer.toString(housecode);
String unitstring = Integer.toString(unitcode);
String onoffstring = Integer.toString(onoff);
ProcessBuilder builder = new ProcessBuilder("/bin/bash", "-c", "sudo /home/pi/rcswitch-pi/send", housestring, unitstring, onoffstring);
Process proc = builder.start();
BufferedReader reader =
new BufferedReader(new InputStreamReader(proc.getInputStream()));
String line = "";
while((line = reader.readLine()) != null) {
System.out.print(line + "\n");
}
}
However, it doesn't seem like the terminal is receiving the command as it does not output anything. It should show something like "command received" and execute it then. When I normally execute the /send command in the terminal it works just fine. In eclipse it just works fine and throws the expected error.
Thanks for your answers :)
It is most likely that an error has occured while executing the command. Keep in mind that Process#getInputStream() does not include standard error stream of the process. You should use Process#getErrorStream(). Something like:
BufferedReader reader = new BufferedReader(new InputStreamReader(proc.getErrorStream()));
String line = null;
while((line = reader.readLine()) != null) {
System.out.print(line + "\n");
}
Related
I use this method call_shell() to connect Java and shell.
private static String call_shell(String command) throws IOException, InterruptedException{
Process proc = Runtime.getRuntime().exec(command);
if(proc.waitFor() != 0){
System.out.println("wrong in shell.");
}
String s = null;
StringBuilder sb = new StringBuilder();
BufferedReader br = new BufferedReader(new InputStreamReader(proc.getInputStream()));
while((s = br.readLine()) != null){
sb.append(s).append("\r\n");
}
br.close();
return sb.toString();
}
However, when I call this method using System.out.println(call_shell("/usr/local/bin/redis-server"));, it will get blocked on the console, because of redis-server will block the bash.
So I use System.out.println(call_shell("/usr/local/bin/redis-server &")); and want to run it background. However, it turns out an error which is
wrong in shell.
24759:C 21 Apr 16:45:47.718 # Fatal error, can't open config file '&'
How can I run it background?
I am attempting to generate a list of all installed Programs on my Windows machine.
This is the command I am using:
WMIC /output:D:\miep product get name && type D:\miep > D:\miep_
You might have realized that I'm also trying to make a type-Command as I need the output in UTF-8.
I made a Whitelist for this with a simple loop where I will look later where in my file certain Names will appear and keep them while I remove everything else.
The command works in the command prompt, but when I try to do the same inside my Java Program it keeps telling me I've got an Invalid GET-Expression ...
Here is my function:
void createLists() throws IOException {
//String cmd = "WMIC /output:D:\\miep.csv product get name /format:\"%WINDIR%\\System32\\wbem\\de-DE\\csv.xsl\"";
String cmd = "WMIC /output:D:\\miep product get name && type D:\\miep > D:\\miep_";
System.out.println(cmd);
Process p;
p = Runtime.getRuntime().exec(cmd);
p.getOutputStream().close();
String line;
BufferedReader stdout = new BufferedReader(new InputStreamReader(p.getInputStream()));
while ((line = stdout.readLine()) != null) {
System.out.println(line);
}
stdout.close();
BufferedReader stderr = new BufferedReader(new InputStreamReader(p.getErrorStream()));
while ((line = stderr.readLine()) != null) {
System.out.println(line);
}
stderr.close();
System.out.println("Done");
}
I also tried the converting stuff with the .csv files as you might have seen in the second line of my code and the same:
Works in CMD, but not in my Java-Program..!
Here it keeps telling me that it's an Invalid XSL-Format
Can someone help?
I have a weird problem when trying to execute a shell command from within a java program. Since there exist thousands of websites that explain how to do it I used the following recommended code:
public String executeShellCommand (String command)
{
try
{
StringBuffer sb = new StringBuffer();
String line = "";
Process p = Runtime.getRuntime().exec(command);
BufferedReader reader = new BufferedReader(new InputStreamReader(
p.getInputStream()));
while ((line = reader.readLine()) != null)
sb.append(line + "\n");
p.waitFor();
return sb.toString();
}
catch (Exception e)
{
e.printStackTrace();
}
return null;
}
Acutally, when I try to execute for instance ls -aF is works fine and I get some output as a result. Therefore I'm pretty sure that the above code is, in principal, correct. However, I got another program I'd like to run and that produces a file as an output. I would like to execute it the above way but it never is executed and no output file is generated. Also I do not get any error, warnings or whatsoever in java. When copy and pasting the actual command argument string into the console the execution of the programm/command directly in the shell works fine and the output file is generated. So the command I pass to the method is also correct.
Are there additional things I need to pay attention to when trying to execute a shell command from within java?
UPDATE: I modified my code according to the suggestions. However, it is still hanging:
public String executeShellCommand(List<String> command, String logfile, boolean waitForProcess) { try {
ProcessBuilder pb = new ProcessBuilder(command);
System.out.println("pb.toString() = " + pb.toString());
Process p = pb.start();
System.out.println("2");
BufferedReader err = new BufferedReader(new InputStreamReader(p.getErrorStream()));
BufferedReader out = new BufferedReader(new InputStreamReader(p.getInputStream()));
System.out.println("3");
StringBuilder errSb = new StringBuilder();
StringBuilder outSb = new StringBuilder();
String line;
System.out.println("4");
while ((line = err.readLine()) != null) { // <--- code hangs here
errSb.append(line + "\n");
System.out.println("errSb = " + errSb.toString());
}
System.out.println("4a");
while ((line = out.readLine()) != null) {
outSb.append(line + "\n");
System.out.println("outSb = " + outSb.toString());
}
System.out.println("5");
if(waitForProcess) {
System.out.println("Wait for process");
p.waitFor();
} else {
System.out.println("Sleep 5000");
Thread.sleep(5000);
}
System.out.println("6");
//Log result to file
if(logfile != null) {
OutputStreamWriter outWriter = new OutputStreamWriter(new FileOutputStream(logfile));
outWriter.write(errSb.toString());
outWriter.close();
}
return errSb.toString();
} catch(Exception e) { e.printStackTrace(); } return null; }
This will block if your command writes too many characters to stderr. Like for sdtout, Java redirect stderr through a pipe, and if you do not read the pipe, it can fill up and block (size of the pipe is probably less than 256 bytes). To avoid that, you need to read from the Process.getErrorStream(), preferable from another thread as the main thread is busy reading from the Process.getInputStream().
A simpler way to avoid that is to use the ProcessBuilder class instead of Runtime.exec() and ProcessBuilder.redirectErrorStream(true) so that both stdout and stderr are merged into the Process.getInputStream()
As per Process javadoc :
Because some native platforms only provide limited buffer size for standard input and output streams, failure to promptly write the input stream or read the output stream of the subprocess may cause the subprocess to block, or even deadlock.
You are calling p.waitFor(). If we carefully read the waitFor() documentation:
Causes the current thread to wait, if necessary, until the process represented by this Process object has terminated.
You are waiting for a process which hangs, because its error stream and output stream are never read.
What you should do, is to read these streams:
p.start();
BufferedReader err= new BufferedReader(new InputStreamReader(p.getErrorStream()));
BufferedReader out = new BufferedReader(new InputStreamReader(p.getOutputStream()));
StringBuilder errSb = new StringBuilder();
StringBuilder outSb = new Stringbuilder();
String line;
while ((line = err.readLine()) != null) {
errSb.append(line);
}
while ((line = out.readLine()) != null) {
outSB.append(line);
}
int retCode = p.waitFor(); //0 for success
System.out.println(retCode);
System.err.println(errSB.toString());
You should always read the error stream when calling external programs via the Process class, else you may find yourself in this odd situation where a process hangs forever. (well until someone else -the operating system, another application, etc- kills it, more exactly).
I've also noticed that you use the Runtime.getRuntime() which is not the recommended way to run external programs, starting with java 1.5, as per javadoc:
As of 1.5, ProcessBuilder.start() is the preferred way to create a Process.
ProcessBuilder pb = new ProcessBuilder("ls" , "-aF");
Process p = pb.start();
In Java, I want to be able to execute a Windows command.
The command in question is netsh. This will enable me to set/reset my IP address.
Note that I do not want to execute a batch file.
Instead of using a batch file, I want to execute such commands directly. Is this possible?
Here is my implemented Solution for Future Reference:
public class JavaRunCommand {
private static final String CMD =
"netsh int ip set address name = \"Local Area Connection\" source = static addr = 192.168.222.3 mask = 255.255.255.0";
public static void main(String args[]) {
try {
// Run "netsh" Windows command
Process process = Runtime.getRuntime().exec(CMD);
// Get input streams
BufferedReader stdInput = new BufferedReader(new InputStreamReader(process.getInputStream()));
BufferedReader stdError = new BufferedReader(new InputStreamReader(process.getErrorStream()));
// Read command standard output
String s;
System.out.println("Standard output: ");
while ((s = stdInput.readLine()) != null) {
System.out.println(s);
}
// Read command errors
System.out.println("Standard error: ");
while ((s = stdError.readLine()) != null) {
System.out.println(s);
}
} catch (Exception e) {
e.printStackTrace(System.err);
}
}
}
Runtime.getRuntime().exec("netsh");
See Runtime Javadoc.
EDIT: A later answer by leet suggests that this process is now deprecated. However, as per the comment by DJViking, this appears not to be the case: Java 8 documentation. The method is not deprecated.
Use ProcessBuilder
ProcessBuilder pb=new ProcessBuilder(command);
pb.redirectErrorStream(true);
Process process=pb.start();
BufferedReader inStreamReader = new BufferedReader(
new InputStreamReader(process.getInputStream()));
while(inStreamReader.readLine() != null){
//do something with commandline output.
}
You can run the command with Runtime.getRuntime().exec("<command>") (eg. Runtime.getRuntime().exec("tree")). But, this will only run executables found in path, not commands like echo, del, ... But only stuff like tree.com, netstat.com, ... To run regular commands, you will have to put cmd /c before the command (eg Runtime.getRuntime().exec("cmd /c echo echo"))
public static void main(String[] args) {
String command="netstat";
try {
Process process = Runtime.getRuntime().exec(command);
System.out.println("the output stream is "+process.getOutputStream());
BufferedReader reader=new BufferedReader( new InputStreamReader(process.getInputStream()));
String s;
while ((s = reader.readLine()) != null){
System.out.println("The inout stream is " + s);
}
} catch (IOException e) {
e.printStackTrace();
}
}
This works.
Runtime#exec().
Is there a way using Java that I can gain a list of all active processes running on a Mac?
I can do so in Windows using the code below to return the Task List, but that throws an exception on a Mac. I want my app to stop if certain applications are also running.
Any ideas? Thanks.
Windows Code:
Process p = Runtime.getRuntime().exec("tasklist.exe /nh");
BufferedReader input = new BufferedReader
(new InputStreamReader(p.getInputStream()));
//while there are more processes in the task manager list
while ((line = input.readLine()) != null) {
//insert code here for each task running
}
String line;
String sysUserName=System.getProperty("user.name");
Process p = Runtime.getRuntime().exec("tasklist /fi \"username eq"+sysUserName+"\""); // for windows
// Process p = Runtime.getRuntime().exec("ps -u "+sysUserName+""); // for mac
BufferedReader input =
new BufferedReader(new InputStreamReader(p.getInputStream()));
while ((line = input.readLine()) != null) {
System.out.println(line); //<-- Parse data here.
}
input.close();
tasklist.exe does not exist on Mac. Use something like ps -eaf