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Error when creating zstd file with ProcessBuilder on Java

I'm trying to use ProcessBuilder in order to create a tar.zst file that compresses a folder. However, I'm getting the following error after running this code:
try {
ProcessBuilder pb = new ProcessBuilder("tar","--zstd","-cf","info-x.tar.zst","tstpkg");
pb.redirectOutput(ProcessBuilder.Redirect.INHERIT);
pb.redirectError(ProcessBuilder.Redirect.INHERIT);
Process process = pb.start();
process.waitFor();
} catch (Exception e){
e.printStackTrace();
}
Error:
tar: Can't launch external program: zstd --no-check -3
And the tar file is created, but is empty.
If I run the same command from the terminal
tar --zstd -cf info-x.tar.zst tstpkg
then it works fine.

When you find a command that works "from the terminal" but not from Java then you should assume that the PATH or other environment required with that command is only set correctly via that terminal, and not when called by JVM.
So, one possible fix is to run your terminal indirectly which may fix the environment needed - depending on your shell and it's setup:
ProcessBuilder pb = new ProcessBuilder("bash", "-c", "tar --zstd -cf info-x.tar.zst tstpkg");
You might also try to fix by setting the correct PATH for running zstd as a sub-process of tar. Check where it is using which zstd and try adding to the PATH before pb.start():
String path = pb.environment().get("PATH"); // use Path on Windows
pb.environment().put("PATH", "/path/to/dir/ofzstd"+File.pathSeparator+path);

"Error: Unable to access jarfile" command executed using Runtime exec

I am developing a Java application where one of its task is to execute a system command using Runtime exec. The command requires another JAR file to be able to work but whenever the part where the command will be executed, I am getting an "Error: Unable to access jarfile".
Firstly, my current working directory:
assets/jarFile.jar
myApp.jar
Here's what my code looks like:
try {
// To get the path of the directory where my current running JAR is
String jarPath = myApp.class.getProtectionDomain().getCodeSource().getLocation().getPath();
String path = URLDecoder.decode(jarPath.substring(0, jarPath.lastIndexOf("/")), "UTF-8");
// The system command to execute
String command = "java -Xmx1024m -jar "+path+"/assets/jarFile.jar and-so-on...";
Process p = Runtime.getRuntime().exec(command);
...
}
The jarFile.jar is not an executable JAR by the way.
Any idea?

Seems like your code to find the path of the jar file does not return the correct path.

executing bash commands from a specific directory

From my application I have to execute an external jar of which I do not have the source.
Given an input file, it processes it, creates an "output" directory and puts in it an mxml output file. Problem is: it creates said directory in tomcat/bin instead of inside the directory of the original file.
Here's what I've tried so far.
Initially
Process p = new ProcessBuilder("java -jar "+newfile.getParent()+"\\converter.jar "+newfile.getPath()+" -mxml").start();
Then, seeing how from console the "output" directory was created in the directory the command was called from, I tried:
String startSim[] = {"cd "+newfile.getParent()+"\\" , "java -jar converter.jar "+newfile.getName()+" -mxml"};
try {
Runtime.getRuntime().exec(startSim).waitFor();
} catch (Exception e) {
e.printStackTrace();
System.out.println("Log non creato.");
}
But with this I get the "file not found" exception for the first instruction. Does anyone know how to possibly solve this problem? I'd like to avoid having to reach for my output file all the way in my tomcat/bin directory.
Thanks for any suggestion!
Paolo
P.s.: by the way, before trying all this I tried simply calling the method I need from the library, but had the same exact problem. So I resolved to execute the jar, instead. And here we are. :)

You can set working directory using ProcessBuilder.directory() method:
ProcessBuilder pb = new ProcessBuilder();
pb.directory(new File("mydirectory"));
pb.command(......);
etc
This does not work for you when you are using Runtime.exec() because cd command is a functionality of shell. You could solve it using this technique but you have to create platform specific command with prefix like cmd /c on windows or /bin/sh on Linux. This way is definitely not recommended.
But in your specific case you do not neither first nor second solution. Actually you are starting one java process from another. Why? you can easily invoke the main() method of the second process directly.
Take a look on META-INF/MANIFEST.mf file from converter.jar. Field Main-Class contains the fully qualified name of main class. Let's say it is com.converters.Main (just for example). In this case you can invoke
com.converters.Main.main(new String[] {newFile.getPath(), "-mxml"});
directly from your code. Just add the jar to your classpath.
Concerning to changing working directory in this case. Check again whether you really need this or your converters.jar supports parameter that does this.

A lazy approach to this may be going to the root directory and descending from there to your tomcat bin directory .

C program compilation from a java program

I am trying to compile a c program from a java program on Linux platform. My snippet is.
ProcessBuilder processBuilder = new ProcessBuilder("/usr/bin/gcc",
"-c","/hipad/UserProject/example.c");
Process proc = processBuilder.start();
There is no error during compilation of java program but I am not able to get .o file. I tried to find out solutions but no one is working.
Any suggestion.....

The default working directory of a child process is what ever directory the Java process has as a working directory, which usually is where it was launched from. And by default gcc writes output files to current working directory. That's where you should find example.o.
There are two simple ways to solve this. You can give gcc -o option and full path and name of desired output file, or you can set working directory of child process, like this:
ProcessBuilder processBuilder =
new ProcessBuilder("/usr/bin/gcc", "-c","example.c"); // source in working dir
processBuilder.directory(new File ("/hipad/UserProject")); // or whatever
Process proc = processBuilder.start();
See ProcessBuilder javadoc for more info.

Change PWD of linux from JSP

I need to execute linux commands from JSP.
It is working fine.
But i need to start some sh file in a particular directory in linux through JSP. say /home/username/something/start.sh
try{
String command= "cd /home/username/something";
Runtime.getRuntime().exec(command);
Runtime.getRuntime().exec("./start.sh")
out.println("Child");
}
catch(Exception e)
{ out.println("Error");
}
It says FIle or Directory not found.
I tried Runtime.getRuntime().exec("pwd"), It is showing something like "java.lang.UNIXProcess#fc9d2b" !! :O
I need to change the pwd and execute some commands through jsp. How can i do that??
Any help would be appreciated.

You shouldn't (and actually, it seems you can't) set a working directory like that. Each Process object given by Runtime.exec() will have its own working directory.
As answered in How to use “cd” command using java runtime?, you should be using the three argument version of Runtime.exec(), in which you provide a File that will be the working directory. From its javadoc:
Executes the specified command and arguments in a separate process with the specified environment and working directory.
Or even better, use ProcessBuilder along with ProcessBuilder.directory() instead:
ProcessBuilder pb = new ProcessBuilder("start.sh");
pb.directory(new File("/home/username/something"));
Process p = pb.start();