I have two jar files named test1.jar and test2.jar.
In order to execute a function in in this jar file, I run below command in cmd.
“java getOutput argument1 argument2 argument3 argument4”
As a pre-requisite, I have set the following entries in my system environment variables to execute the java function using the above command.
1.CLASSPATH=C:\Folder\test1.jar;C:\Folder\test2.jar;C:\Program Files\Java\jre1.8.0_181\lib\plugin.jar
2.JAVA_BIN=C:\Program Files\Java\jre1.8.0_181\bin
3.JAVA_HOME=C:\Program Files\Java\jre1.8.0_181
4.PATH = C:\Program Files\Java\jre1.8.0_181\bin
The output of the above command is a string.
I have another java code. I have to capture the above string output in a variable in my java program and I am able to do this by using below java code in eclipse.
String strArgs= strArg1+" "+strArg2+" "+strArg3+" "+strArg4;
Process p=Runtime.getRuntime().exec("cmd /c java getOutput "+strArgs+"");
BufferedReader input =new BufferedReader(new
InputStreamReader(p.getInputStream()));
String strOutput = input.readLine();
if (strOutput != null) {
System.out.println(strOutput);
String strVariable = strOutput;
input.close();
}else {
System.out.println("FAIL- Output not generated");
}
In order to execute the above code on unix, I replace Line 2 with "Process p=Runtime.getRuntime().exec("usr/bin/java getOutput "+strArgs+"");" , convert the eclipse java project into a jar file named automation.jar. And I try to execute this jar file on unix using the below command .
`java -cp automation.jar Package.MainClass.'
When I run the code I get the output as null. But when I run the command on windows command prompt I get the output string.
Could you please help me on how to set the system variables in unix and perform the above operation to generate the string output.
Please let me know if any additional information required.
cmd is windows only. Unix uses a shell. But you shouldn't need either here. Just remove the cmd call.
Process p = Runtime.getRuntime().exec("java getOutput " + strArgs);
If it can't find Java, you can read the JAVA_BIN (or JAVA_HOME) from the environment.
String java_bin = System.getenv("JAVA_BIN");
Process p = Runtime.getRuntime().exec(java_bin + "/java getOutput " + strArgs);
Finally, your environment variables look like Windows path variables. Make sure they're correct for your Unix environment (Unix doesn't have a "C" drive).
I am running Java program to call Python process using process builder as shown below,
processBuilder = new ProcessBuilder(
Arrays.asList(
"/usr/bin/python",
"/opt/gui/oc_db5.py",
"-c",
"/opt/gui/test.json")
);
processBuilder.directory(new File("/opt/gui"));
processBuilder.start();
Location of python program is under /opt/gui directory and there is one test.json file also needs to be passed as parameter, with "-c" option, However what i am seeing is that system is appending location of java program with path of JSON file and then pick the .JSON file causing issue for Python code.
What actually python program is getting is /opt/java//opt/gui/test.json. I tried ../../ as well but it didn't work with test.json file.
Is there a way i can specify .JSON file as an argument to python program?
This seemed to work for me. I mean, it fixed the directory problem.
try {
int exitCode = Runtime.getRuntime().exec("python /opt/gui/oc_db5.py -c /opt/gui/test.json", null, new File("/")).waitFor(); // run program and get exit code
} catch(Exception e) { // is there an error?
e.printStackTrace(); // print error
}
i'm trying to execute a SOX command from java, but unfortunately its returning an error everytime. Every other SOX commands are working perfectly though!!
Here is the code :
class Simple {
public static void main(String args[]) throws IOException, Exception {
Process p;
BufferedReader br;
String co = "sox speech_16.wav -p pad 0 2.5 | sox - -m speech_16.wav speech_output.wav";
p = Runtime.getRuntime().exec(co);
br = new BufferedReader(new InputStreamReader(p.getInputStream()));
int returnCode = p.waitFor();
System.out.println("reurn code : "+returnCode);
}
}
When I'm executing the same sox command in terminal, its working fine. I really can't understand what the problem is!! Is it because of the '|' symbol??
The issue is that Runtime.exec() does not understand shell concepts such as "|". Instead try:
Runtime.getRuntime().exec("/bin/sh", "-c", co);
The problem is that exec runs a binary directly without invoking the shell. The "|" character is only recognized by the shell, not by sox. The "-c" tells the shell to run a single command, and passes the entire command as the single argument.
This is likely to be related to the environment in which the commands get executed, it could be any of the following:
The sox executable cannot be found (put the full path in the command)
The user does not have permission to run the sox command (check execute bit in file permissions)
Some environment variable needed by sox is not initialised when you run the command from Java (check sox documentation)
If speech_16.wav is an input file to sox then the file cannot be found (add full path of .wav file to command)
If sox needs to create an output file then it does not have permission to do so, either due to directory permissions, of because there is an existing file with that name which cannot be overwritten, or due to lack of space on the file-system.
From my java project I want to run an external .bat file in another thread. For this purpose I use the following method:
private void posAppRunner(final String path[], final Class targetClass) {
new Thread(new Runnable() {
public void run() {
try {
String line;
Process p = Runtime.getRuntime().exec(path);
BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream()));
while ((line = input.readLine()) != null) {
System.out.println(line);
}
input.close();
} catch (IOException e) {
LogFactory.getLog(targetClass).warn("Error when starting a PosApplication: " + e.getMessage());
}
}
}).start();
I run the following .bat file:
call chdir %~dp0
start java <_some_arguments>
So when I do it locally from IntelliJ IDEA it works correct - a cmd process appears, after that a java process appears and after that the cmd process disappears.
But when I run my java project with this method through ANT under TeamCity windows service, only cmd process appears and nothing happens after. Java process that must be started from the bat file doesn't appear. It looks like I don't read the process output but I do!
Could you expain me, how to overcome this situation?
I believe that the problem is in current working directory. I am not so familiar with bat files and do not remember by heart what does %~dp0 mean. Anyway as the first attempt try to modify your batch file to contain the hard coded path. I believe that this will work.
In this case decide what is better for you: discover the path in java code and then pass it to batch file, generate batch file on the fly, so that it contains all parameters hard coded or debug the script. for example you can remove the start java <_some_arguments> and put
echo %~dp0 > c:\temp\batlog.log
this will print the parameter to log file. Now run it as service and see what does the log file contain. Probably you will see the problem immediately.
I've created a standalone java application in which I'm trying to change the directory using the "cd" command in Ubuntu 10.04 terminal. I've used the following code.
String[] command = new String[]{"cd",path};
Process child = Runtime.getRuntime().exec(command, null);
But the above code gives the following error
Exception in thread "main" java.io.IOException: Cannot run program "cd": java.io.IOException: error=2, No such file or directory
Can anyone please tell me how to implement it?
There is no executable called cd, because it can't be implemented in a separate process.
The problem is that each process has its own current working directory and implementing cd as a separate process would only ever change that processes current working directory.
In a Java program you can't change your current working directory and you shouldn't need to. Simply use absolute file paths.
The one case where the current working directory matters is executing an external process (using ProcessBuilder or Runtime.exec()). In those cases you can specify the working directory to use for the newly started process explicitly (ProcessBuilder.directory() and the three-argument Runtime.exec() respectively).
Note: the current working directory can be read from the system property user.dir. You might feel tempted to set that system property. Note that doing so will lead to very bad inconsistencies, because it's not meant to be writable.
See the link below (this explains how to do it):
http://alvinalexander.com/java/edu/pj/pj010016
i.e. :
String[] cmd = { "/bin/sh", "-c", "cd /var; ls -l" };
Process p = Runtime.getRuntime().exec(cmd);
Have you explored this exec command for a java Runtime, Create a file object with the path you want to "cd" to and then input it as a third parameter for the exec method.
public Process exec(String command,
String[] envp,
File dir)
throws IOException
Executes the specified string command in a separate process with the specified environment and working directory.
This is a convenience method. An invocation of the form exec(command, envp, dir) behaves in exactly the same way as the invocation exec(cmdarray, envp, dir), where cmdarray is an array of all the tokens in command.
More precisely, the command string is broken into tokens using a StringTokenizer created by the call new StringTokenizer(command) with no further modification of the character categories. The tokens produced by the tokenizer are then placed in the new string array cmdarray, in the same order.
Parameters:
command - a specified system command.
envp - array of strings, each element of which has environment variable settings in the format name=value, or null if the subprocess should inherit the environment of the current process.
dir - the working directory of the subprocess, or null if the subprocess should inherit the working directory of the current process.
Returns:
A new Process object for managing the subprocess
Throws:
SecurityException - If a security manager exists and its checkExec method doesn't allow creation of the subprocess
IOException - If an I/O error occurs
NullPointerException - If command is null, or one of the elements of envp is null
IllegalArgumentException - If command is empty
This command works just fine
Runtime.getRuntime().exec(sh -c 'cd /path/to/dir && ProgToExecute)
Using one of the process builder's method we could pass the directory where we expect the cmd to be executed. Please see the below example. Also , you can mention the timeout for the process, using wait for method.
ProcessBuilder builder = new ProcessBuilder("cmd.exe", "/c", cmd).directory(new File(path));
Process p = builder.start();
p.waitFor(timeoutSec, TimeUnit.SECONDS);
In the above code, you can pass the file object of the path[where we expect the cmd to be executed] to the directory method of ProcessBuilder
My preferred solution for this is to pass in the directory that the Runtime process will run in. I would create a little method like follows: -
public static String cmd(File dir, String command) {
System.out.println("> " + command); // better to use e.g. Slf4j
System.out.println();
try {
Process p = Runtime.getRuntime().exec(command, null, dir);
String result = IOUtils.toString(p.getInputStream(), Charset.defaultCharset());
String error = IOUtils.toString(p.getErrorStream(), Charset.defaultCharset());
if (error != null && !error.isEmpty()) { // throw exception if error stream
throw new RuntimeException(error);
}
System.out.println(result); // better to use e.g. Slf4j
return result; // return result for optional additional processing
} catch (IOException e) {
throw new RuntimeException(e);
}
}
Note that this uses the Apache Commons IO library i.e. add to pom.xml
<dependency>
<groupId>commons-io</groupId>
<artifactId>commons-io</artifactId>
<version>2.10.0</version>
</dependency>
To use the cmd method e.g.
public static void main(String[] args) throws Exception {
File dir = new File("/Users/bob/code/test-repo");
cmd(dir, "git status");
cmd(dir, "git pull");
}
This will output something like this: -
> git status
On branch main
Your branch is up to date with 'origin/master'.
nothing to commit, working tree clean
> git pull
Already up to date.
Try Use:
Runtime.getRuntime.exec("cmd /c cd path");
This worked
Runtime r = Runtime.getRuntime();
r.exec("cmd /c pdftk C:\\tmp\\trashhtml_to_pdf\\b.pdf C:\\tmp\\trashhtml_to_pdf\\a.pdf cat output C:\\tmp\\trashhtml_to_pdf\\d.pdf");
The below did not work
While using array command did NOT WORK
String[] cmd = {"cmd /c pdftk C:\\tmp\\trashhtml_to_pdf\\b.pdf C:\\tmp\\trashhtml_to_pdf\\a.pdf cat output C:\\tmp\\trashhtml_to_pdf\\d.pdf"}; r.exec(cmd);
FYI am using utility to check OS if its windows above will work for other than windows remove cmd and /c
I had solved this by having the Java application execute a sh script which was in the same directory and then in the sh script had done the "cd".
It was required that I do a "cd" to a specific directory so the target application could work properly.