i have written a code to run .dat file using Java. but when is run that application then it take time to execute means it give half result and then after some time after gives complete result.
here is my code:
String file = config.getOutPath() + "run_doxygen.bat";
BufferedWriter out = new BufferedWriter(
new FileWriter(file));
String cmd = "doxygen " + config.getOutPath() + "Doxyfile";
runtime.exec(cmd);
System.out.println("cmd_doxy:"+cmd);
out.write(cmd);
out.newLine();
out.close();
the doxygen generate xml file. let suppose it generate 10 xml file . when i launch that *.bat file it generate 5 file and to generate rest 5 file it take time.
and *.bat file contain : doxygen "path"
path is location of config file. it work fine when i run it with cmd or double click.
anybody have any idea
.
thanks
May be you should flush the writer.
out.newLine();
out.flush();
out.close();
It is not entirely clear what you intend your program to do, but what it is actually is doing is as follows:
It opens the ".bat" file for writing.
It launches a "doxygen" command as a separate external process.
It writes the command to standard output, and then the file.
If you are saying that it takes some time for the output to be written to the file, well that is not entirely unexpected. The operating system may decide to give the newly launched doxygen application a big chunk of CPU time to get started. If it doesn't block, your Java application may not get a time-slice for a few seconds. And after that, the OS may switch between the two applications until one or the other finishes.
But why does it matter? Does your Java application expect / require doxygen to finish before it does?
If so, then the solution is to do something like this:
Process proc = runtime.exec(cmd);
// do more stuff.
int rc = proc.waitFor();
// Whoopee! the process has finished (or died) check the rc to see which.
if you are not consuming the streams generated by the external command, it can cause the program to hang. See this article which pretty much covers all the gotchas of using Runtime.exec.
Related
I have sample java code like below.
String testEfdDirectoryPath="D:\\test";
String efdExecutable = "test.cmd";
File executableFile = new File(testEfdDirectoryPath, efdExecutable);
ProcessBuilder pb=new ProcessBuilder();
$$pb.command("cmd.exe","/C",executableFile.toString());$$
pb.directory(new File(testEfdDirectoryPath));
Process p=pb.start();
int code=p.waitFor();
System.out.print(code);
In test.cmd there is actually a call to another java application. Unless I change the $$ marked line to the following to redirect its output, the another java app cannot be launched.
pb.command("cmd.exe","/C",executableFile.toString(),">output.txt");
Do you guys have any ideas? Thanks in advance. :)
Does your child process produce a lot of output (more than a few kilobytes)? If that is the case, you need to read that output from the process. You should try:
start the process
close the stdin of the process, so pb.getOutputStream().close()
repeatedly read from pb.getInputStream() and the error stream
This may be possible in one thread, or in multiple threads. Anyway, you should just take the explanation above as a list of keywords and try to search for an example code snippet that you can trust, preferrably from an Open Source application that does such a thing successfully.
Maybe http://commons.apache.org/exec/ can help you.
Windows cannot execute scripts directly; when you double click on a .cmd file it actually opens the file in cmd.exe. So try cmd.exe E:\\test\\test.cmd.
I'm making an update function for my project, it's working great, until i want it to restart, basically I download the new file and replace it with the old one, and then i want to run it again, now for some reason it doesn't wna run, and i don't get any error...
Here is the complete update class:
http://dl.dropbox.com/u/38414202/Update.txt
Here is the method i'm using to run my .jar file:
String currDir = new File("(CoN).jar").getAbsolutePath();
Process runManager = Runtime.getRuntime().exec("java -jar " + currDir);
It's not clear to me, why do you need to run the jar with a call to exec() . Given that you need to run the code in the .jar file from a Java program, you could simply run the main() method as defined in the jar's manifest, and capture its output - wherever that is.
Using exec() is OK when you need to call a program from the underlying operating system, but there are easier ways to do this if both the caller and the callee are Java programs.
Now, if your jar is gonna change dynamically and you need to update your program according to a new jar, there are mechanisms for reloading its contents, for instance take a look ath this other post.
The JavaDocs for the Process class specifically point out that if you don't capture the output stream of the Process and promptly read it that the process could halt. If this is the case, then you wouldn't see the process that you started run.
I think you have to capture the stream like this :
BufferedReader stdInput = new BufferedReader(new InputStreamReader(runManager.getInputStream()),8*1024);
BufferedReader stdError = new BufferedReader(new InputStreamReader(runManager.getErrorStream()));
// read the output from the command
String s = null;
System.out.println("Here is the standard output of the command:\n");
while ((s = stdInput.readLine()) != null) {
System.out.println(s);
}
The exec function doesn't automatically lookup into the PATH to start a process, so you have to pass the complete path for the java binary.
You can do that by using the java.home system property, see this answer: ProcessBuilder - Start another process / JVM - HowTo?
No one here seemed to help me, so I went to ask my friend and I had it almost right. It abiously required the string to be an array.
solution:
String[] cmd = {"java", "-jar", currDir};
try {
Runtime.getRuntime().exec(cmd);
} catch (IOException e1) {
e1.printStackTrace();
}
I am looking for a help regarding a shell script to redirect the output of a command to a file. I have a C program that reads the input from a serial port and display. I want this data to be redirected to a file. I am executing this from a java program by calling
Runtime r = Runtime.getRuntime();
Process procObj = r.exec("sh " + scriptfile);
I have tried writing the script file as
./program >> file.txt
The file.txt is not getting updated. Here, the program doesn't end until the connection to the port is lost, in a sense it is infinitely running. So my program keeps looking for data on the port and display as and when it is there.
I just need to redirect the same output to a file that I would use as a log.
I looked at How to make shell output redirect (>) write while script is still running? but not helpful.
Kindly help..
How much output does program generate? Using standard IO redirection will add a 4KB buffer between stdout and file. This means your program must output more than 4KB of data before the OS starts to write to the file.
To fix this, add stdout.flush() to your program when a "work unit" is complete (maybe a line but might be more than one line).
Can you try ./program >> file.txt 2>>file.txt, or ./program 2>&1 >>file.txt?
just try this
List<String> cmd = new ArrayList<String>();
cmd.add("sh");
cmd.add("-c");
cmd.add("program 1> file.txt 2>&1");
ProcessBuilder pb = new ProcessBuilder(cmd);
Process p = pb.start();
If you use standard C calls for output (printf, puts etc.), your output may get buffered. On C89 and onwards, it depends on the buffering mode (unbuffered, fully buffered, line buffered) and on the size of the buffer, whether your output is buffered at all and when the buffer is flushed (see http://www.gnu.org/software/libc/manual/html_node/Buffering-Concepts.html and man setvbuf).
By default, output to a file is fully buffered on Linux. If you want the output to appear immediately in the output file, you may:
use fflush() after each output operation
use the system call write() (man 2 write)
switch off buffering: setvbuf(stdout, NULL, _IONBF, 0); (https://stackoverflow.com/a/7876756/601203)
This behaviour is not related on the fact the you start your C program in a Java program via a shell script. This behaviour depends on the standard C library that you have linked into your program.
When I try to execute an external program from java I use this code below :
Process p;
rn = Runtime.getRuntime();
String[] unzip = new String[2];
unzip[0]="unzip";
unzip[1]=archive ;
public void dezip() throws IOException{
p = rn.exec(unzip);
int ret = p.exitValue();
System.out.println("End of unzip method");
But my last System.out is never executed, as if we exit from unzip method.
The unzip() call does only the half of the work, only a part of my archive is unzipped.
When I use ps -x or htop from command line I see that unzip process is still here.
Help please.
You probably need to read the InputStream from the process. See the javadoc of Process
Which states:
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, and even deadlock.
Check if the unzip command is prompting for something, perhaps a warning if the file already exists and if you want to overwrite it.
Also, is that a backquote I see in the middle of a java program?
Make sure external program doesn't wait for user input
Check if the the executable path is quoted when launching on Windows systems to handle directories with spaces or special characters.
PS.
I was using the java.lang.Runtime class but found that the java.lang.ProcessBuilder class is far superior. You can specify current working directory, and most importantly the system environment.
Please try the following:
p = rn.exec(unzip);
p.waitFor()
I hope it will change something.
I have (in java),
rt.exec("qq.exe -i ..(some other parameters) > qq.log");//*1
when I run qq.exe -i ..(some other parameters) > qq.log in terminal It works fine and keeps the qq.log file correctly.
However using rt.exec (*1) doesnt work. " > qq.log" part causes problem. When I delete that part rt.exec (*1) works but I cant have qq.log file this time.
What causes this problem and Is there any soln??
rt.exec() can't execute sh/bat code. It's just invoking another program. When you try to redirect the output stream of qq.exe with the > symbol, which is specific to shell, java doesn't understand what to do.
An alternative is when you execute some program with the exec method, get the Process returned by rt.exec().
A Process can give you an OutputStream to the application, an InputStream from the application and even an ErrorStream for a started application.
With the InputStream, you can programmatically read the result of qq.exe and all you have to do is to write this into a file.
Java 7 added ProcesBuilder.Redirect class that allows to redirect input/output/error streams to/from files. It can be used like this:
ProcessBuilder builder = new ProcessBuilder("cat", "/proc/meminfo");
// Append all errors from process to log file:
builder.redirectError(Redirect.appendTo(new File("/tmp/my.log")));
Process process = builder.start();
Using corresponding methods you can redirect input and output. The full example is here: Run external process in Java 7.