I dont think this is possible, but I have been using:
Process p = Runtime.getRuntime().exec(command);
to run commands on the command line, but now I have come accross a situation where the command I am running part way through will ask for some user input, for example a username.
This can not be resolved by a argument to the command that is being exec, is there any way I can pass the username to the same command line instance and continue?
---EDIT---
I still cant get this to work. These are the steps on the command line:
C:\someProgram.exe
Login:
Passowrd:
So I need to pass the login and password when it prompts at runtime. The code I've got that doesnt work:
try {
String CMD = "\"C:\\someProgram\"";
Scanner scan = new Scanner(System.in);
ProcessBuilder builder = new ProcessBuilder(CMD);
builder.redirectErrorStream(true);
Process process = builder.start();
InputStream is = process.getInputStream();
BufferedReader reader = new BufferedReader (new InputStreamReader(is));
OutputStream out = process.getOutputStream();
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(out));
String line;
try {
while (scan.hasNext()) {
String input = scan.nextLine();
if (input.toLowerCase().startsWith("login")) {
writer.write("myUsername");
} else if(input.toLowerCase().startsWith("password")){
writer.write("myPassword");
}
writer.flush();
line = reader.readLine();
while (line != null) {
System.out.println ("Stdout: " + line);
line = reader.readLine();
}
if (line == null) {
break;
}
}
process.waitFor();
}
finally {;
writer.close();
reader.close();
}
}
catch (Exception err) {
System.err.println("some message");
}
Ive tried things like:
writer.write("myUsername\n");
Any help, i can see that someProgram.exe is called and running in the processes, but it just hangs.
Just write to p.getOutputStream(). That'll send the username to the process's standard input, which should do what you want.
out = p.getOutputStream();
out.write("fooUsername\n".getBytes());
out.flush();
You should redirect the command input and send your parameters there. Use process.setInputStream(), the write into this stream.
As part your command String, if you are running on Unix/Linux/OSX and maybe PowerShell, you could prepend the cat shell command to have the shell dump the contents of a file into the input stream for your intended executable to read as input.
A command something like cat user_input.txt | myAppWantsInput.pl.
This will take the content of user_input.txt, dump it into standard-in, so when "myAppWantsInput.pl" in your command executes, and reads from standard-in, it will be reading the contents of the file and taking that as input as if entered from the keyboard.
Of course, it you don't know a priori what values you intend to pass, you could generate the files you need dynamically before invoke the command. This won't work if you can't determine all the input you'll want before you run the command.
Related
I'm trying to manage my minecraft server through java but even though i can read outputs easily I can't manage to get commands or even text in:
ProcessBuilder builder = new ProcessBuilder(
"cmd.exe", "/c", "cd C:\\my\\path\\ && java -jar server.jar nogui");
builder.redirectErrorStream(true);
Process p;
p = builder.start();
this.p = p;
BufferedReader r = new BufferedReader(new InputStreamReader(p.getInputStream()));
String line;
while (loop) {
line = r.readLine();
if (line == null) { break; }
System.out.println(line);
}
This works just fine but when I try to send commands it doesn't work at all:
OutputStream os = BotData.minecraftServer.getOutputStream();
BufferedWriter out = new BufferedWriter(new OutputStreamWriter(os));
String stop = "stop";
try {
out.write(stop + "\n");
out.write("\n");
out.flush();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
I've tried with "Command:>>" + stop + "\n"
with or without / before stop etc.
Killing the process, forcibly or not, starting it in a thread I'd then stop...
I can get neither text nor commands to work.
document says commands from cmd should come with a leading /.
Try send /stop instead of stop.
Also mind, the line line = r.readLine(); may never return a null while the process is alive(by default).
OK found it, it is needed to use write() newline() then flush() to send anything to the console.
My second problem was a dead reference to my process.
destroying the process doesn't work, but the stop command does.
using / is useless, \n doesn't replace newline()
I have the following code example below. Whereby you can enter a command to the bash shell i.e. echo test and have the result echo'd back. However, after the first read. Other output streams don't work?
Why is this or am I doing something wrong? My end goal is to created a Threaded scheduled task that executes a command periodically to /bash so the OutputStream and InputStream would have to work in tandem and not stop working. I have also been experiencing the error java.io.IOException: Broken pipe any ideas?
Thanks.
String line;
Scanner scan = new Scanner(System.in);
Process process = Runtime.getRuntime ().exec ("/bin/bash");
OutputStream stdin = process.getOutputStream ();
InputStream stderr = process.getErrorStream ();
InputStream stdout = process.getInputStream ();
BufferedReader reader = new BufferedReader (new InputStreamReader(stdout));
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(stdin));
String input = scan.nextLine();
input += "\n";
writer.write(input);
writer.flush();
input = scan.nextLine();
input += "\n";
writer.write(input);
writer.flush();
while ((line = reader.readLine ()) != null) {
System.out.println ("Stdout: " + line);
}
input = scan.nextLine();
input += "\n";
writer.write(input);
writer.close();
while ((line = reader.readLine ()) != null) {
System.out.println ("Stdout: " + line);
}
Firstly, I would recommend replacing the line
Process process = Runtime.getRuntime ().exec ("/bin/bash");
with the lines
ProcessBuilder builder = new ProcessBuilder("/bin/bash");
builder.redirectErrorStream(true);
Process process = builder.start();
ProcessBuilder is new in Java 5 and makes running external processes easier. In my opinion, its most significant improvement over Runtime.getRuntime().exec() is that it allows you to redirect the standard error of the child process into its standard output. This means you only have one InputStream to read from. Before this, you needed to have two separate Threads, one reading from stdout and one reading from stderr, to avoid the standard error buffer filling while the standard output buffer was empty (causing the child process to hang), or vice versa.
Next, the loops (of which you have two)
while ((line = reader.readLine ()) != null) {
System.out.println ("Stdout: " + line);
}
only exit when the reader, which reads from the process's standard output, returns end-of-file. This only happens when the bash process exits. It will not return end-of-file if there happens at present to be no more output from the process. Instead, it will wait for the next line of output from the process and not return until it has this next line.
Since you're sending two lines of input to the process before reaching this loop, the first of these two loops will hang if the process hasn't exited after these two lines of input. It will sit there waiting for another line to be read, but there will never be another line for it to read.
I compiled your source code (I'm on Windows at the moment, so I replaced /bin/bash with cmd.exe, but the principles should be the same), and I found that:
after typing in two lines, the output from the first two commands appears, but then the program hangs,
if I type in, say, echo test, and then exit, the program makes it out of the first loop since the cmd.exe process has exited. The program then asks for another line of input (which gets ignored), skips straight over the second loop since the child process has already exited, and then exits itself.
if I type in exit and then echo test, I get an IOException complaining about a pipe being closed. This is to be expected - the first line of input caused the process to exit, and there's nowhere to send the second line.
I have seen a trick that does something similar to what you seem to want, in a program I used to work on. This program kept around a number of shells, ran commands in them and read the output from these commands. The trick used was to always write out a 'magic' line that marks the end of the shell command's output, and use that to determine when the output from the command sent to the shell had finished.
I took your code and I replaced everything after the line that assigns to writer with the following loop:
while (scan.hasNext()) {
String input = scan.nextLine();
if (input.trim().equals("exit")) {
// Putting 'exit' amongst the echo --EOF--s below doesn't work.
writer.write("exit\n");
} else {
writer.write("((" + input + ") && echo --EOF--) || echo --EOF--\n");
}
writer.flush();
line = reader.readLine();
while (line != null && ! line.trim().equals("--EOF--")) {
System.out.println ("Stdout: " + line);
line = reader.readLine();
}
if (line == null) {
break;
}
}
After doing this, I could reliably run a few commands and have the output from each come back to me individually.
The two echo --EOF-- commands in the line sent to the shell are there to ensure that output from the command is terminated with --EOF-- even in the result of an error from the command.
Of course, this approach has its limitations. These limitations include:
if I enter a command that waits for user input (e.g. another shell), the program appears to hang,
it assumes that each process run by the shell ends its output with a newline,
it gets a bit confused if the command being run by the shell happens to write out a line --EOF--.
bash reports a syntax error and exits if you enter some text with an unmatched ).
These points might not matter to you if whatever it is you're thinking of running as a scheduled task is going to be restricted to a command or a small set of commands which will never behave in such pathological ways.
EDIT: improve exit handling and other minor changes following running this on Linux.
I think you can use thread like demon-thread for reading your input and your output reader will already be in while loop in main thread so you can read and write at same time.You can modify your program like this:
Thread T=new Thread(new Runnable() {
#Override
public void run() {
while(true)
{
String input = scan.nextLine();
input += "\n";
try {
writer.write(input);
writer.flush();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
} );
T.start();
and you can reader will be same as above i.e.
while ((line = reader.readLine ()) != null) {
System.out.println ("Stdout: " + line);
}
make your writer as final otherwise it wont be able to accessible by inner class.
You have writer.close(); in your code. So bash receives EOF on its stdin and exits. Then you get Broken pipe when trying to read from the stdoutof the defunct bash.
I'm working on reading the output of a script that is invoked using a Java process. However, in the middle of the script run, it will in SOME situations prompt the user to answer y/n to continue. However, after reading many posts on StackOverflow, I'm still stuck with detecting the prompt and then sending the response while the process is still running.
If anyone has any ideas, that would be awesome.
I've tried reading from Scanner class and System.console to no prevail.
Here is a portion of the code I'm using.
Process p;
String file = "./upgrade.sh";
cmds.add(file);
cmds.add(sourcePath);
cmds.add(outputDirectoryPath);
cmds.add(zip);
cmds.add("-c");
//}
pb = new ProcessBuilder(cmds);
pb.directory(new File(binDir));
p = pb.start();
BufferedReader reader = new BufferedReader (new InputStreamReader(p.getInputStream()));
BufferedReader reader2 = new BufferedReader (new InputStreamReader(p.getErrorStream()));
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(p.getOutputStream()));
try
{
String line = reader.readLine();
while (line != null)
{
System.out.println(line);
line = reader.readLine();
}
reader.close();
writer.close();
}
catch (IOException e)
{
e.printStackTrace();
}
p.destroy();
The problem is that you use a BufferedReader. It will only return when it has read a full line, that is a line separator. But if the script asks for something with a prompt, there won't be a line separator! As a result it WILL NOT return.
You have to use some other kind of reader in order to control the process.
I need to open a command prompt from java code and run some commands on the same and after that I need to read that command prompt output in java code in real time.
I have tried with below code but I was not able to read the cmd prompt display/output in java.
File file = new File("D://Projects/quantum");
Process proc = rt.exec("cmd.exe /c start cmd.exe /k \"ping localhost\"", null, file);
try {
BufferedReader br = new BufferedReader(new InputStreamReader(proc.getInputStream()));
StringBuffer buffer = new StringBuffer();
String line = null;
while ((line = br.readLine()) != null) {
System.out.println(line);
}
} catch (IOException ioe) {
ioe.printStackTrace();
}
Check this out
Process p=Runtime.getRuntime().exec("cmd /c dir");
p.waitFor();
BufferedReader reader=new BufferedReader(new InputStreamReader(p.getInputStream()));
String line=reader.readLine();
This is a very fragile implementation of running a Process.
General tips.
Read and implement all the recommendations of When Runtime.exec() won't.
Once that is done, ignore the fact the article explicitly refers to the Runtime.exec() method and establish the Process using a ProcessBuilder, which makes it easier to implement some of the recommendations of the first linked article.
But even then, break the String command into a String[] arguments of command.
In a java program, I am generating an sh script for use on a centOS machine, which will use sox and lame to decode an MP3 audio file, then apply some gain to the file respectively. Im having some issues getting the Process.waitFor() method to do anything other than hang indefinitely. Here is the code:
try
{
// TODO code application logic here
String reviewPath = "/SomeDirectory/";
String fileName = "FileName";
String extension = ".mp3";
StringBuilder sb = new StringBuilder();
sb.append("#!/bin/bash\n");
sb.append("cd " + reviewPath + "\n");
sb.append("lame --decode " + fileName + extension + "\n");
File script = new File(reviewPath + fileName + ".sh");
script.createNewFile();
script.setExecutable(true);
FileWriter writer = new FileWriter(script);
writer.write(sb.toString());
writer.close();
Process p = Runtime.getRuntime().exec(script.getAbsolutePath());
String line;
BufferedReader bri = new BufferedReader
(new InputStreamReader(p.getInputStream()));
BufferedReader bre = new BufferedReader
(new InputStreamReader(p.getErrorStream()));
while ((line = bri.readLine()) != null) {
System.out.println(line);
}
bri.close();
while ((line = bre.readLine()) != null) {
System.out.println(line);
}
bre.close();
p.waitFor();
System.out.println("Done.");
}
catch (Exception e)
{
System.out.println(e.getMessage());
}
The odd part is that when I run the .sh file it generates by hand, it runs and exits nicely, but when I execute it from a process object in java, it never exits. The exitValue of the process is always "Process has not exited". Ive tried adding set -e to the script, and exit to the end of the script. Short of using the kill command (which I dont really think I can do here) Im at a loss as to what is going on here. Any suggestions?
Add something like while(p.getInputStream().read() != -1); after starting the process. The buffer will get filled and the process will stop waiting for something (in this case, your program) to read from it to free up space.
I figured it out! The problem here was indeed that the output streams needed to be flushed for the application to exit, but simply reading from the streams is not enough. I used Suresh Koya's suggestion and used the processBuilder api, and redirected the error stream on the process before starting it, and read from the streams. This fixed the issues I was having :D