execCMD(“cd ~/Desktop/Tmp/Server/ && java -javaagent:lib/Agent.jar -cp ./Dachuang/dachuang.jar:testcase test.Bank”);

Question

package test;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Test{

    public static void execCMD(String cmd){
        StringBuilder result = new StringBuilder();
        try {
            Process p = Runtime.getRuntime().exec(cmd);
            BufferedReader bf = new BufferedReader(new
                    InputStreamReader(p.getInputStream()));
            String line = null;
            while((line=  bf.readLine())!=null) {
                result.append(line+"\n");
            }
        }catch(Exception e) {
            result.delete(0,result.length()-1).append("无效命令");
        };
        System.out.println(result.toString());
    }

    public static void main(String[] args) throws IOException {
        execCMD("cd ~/Desktop/Tmp/Server/ && java -javaagent:lib/Agent.jar -cp ./Dachuang/dachuang.jar:testcase test.Bank");
    }
}

Why I get null result on the console? I mean maybe I cannot execute this method right on some complex commands. I can exec("java --version") etc. some simple commands. I don't know how to pass parameter to this method, my command is [ cd ~/Desktop/Tmp/Server/ ] and [ java -javaagent:lib/Agent.jar -cp./Dachuang/dachuang.jar:testcase test.Bank ].

here is my screen cuts: no output

Answer 1

Java is not a shell. You can use ProcessBuilder . Instead of cd use directory(File) . And System.getProperty("user.home") instead of ~ . Something like

public static void main(String[] args) throws IOException, InterruptedException {
    File f = new File(System.getProperty("user.home"), "Desktop/Tmp/Server/");
    ProcessBuilder pb = new ProcessBuilder().directory(f);
    pb.inheritIO();
    pb.command("java", "-javaagent:lib/Agent.jar",
            "-cp", "./Dachuang/dachuang.jar:testcase", "test.Bank");
    Process p = pb.start();
    p.waitFor();
}

Answer 2

As Elliott says: Java is not a shell. And it doesn't understand shell command syntax. When you exec (or similar) a string with whitespace in it, Java crudely splits it into an array of Strings, ignoring any shell escapes or quotes. Then calls exec(String[]) which treats the first word as command name and the rest as the command's arguments.

If you really want to use shell command syntax (eg && ), and shell builtin commands (eg cd ), you can do this:

public static void main(String[] args) throws IOException, InterruptedException {
    ProcessBuilder pb = new ProcessBuilder();
    
    // Uncomment the next line if you want the child shell to inherit
    // this processes stdin, stdout and stderr streams

    // pb.inheritIO();       

    pb.command("/bin/bash", "-c" 
               "cd ~/Desktop/Tmp/Server/ && java -javaagent:lib/Agent.jar " +
               "-cp ./Dachuang/dachuang.jar:testcase test.Bank");
    Process p = pb.start();
    p.waitFor();
}

This is actually running an instance of bash to run a shell command line. It should work for any command line. (You would need to use normal Java string escapes for any backslash or double-quote characters in the command string. That is because this is a Java string literal...)

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Elliott's answer is a more elegant solution for your example, but if the shell command line is more complicated, that approach gets too difficult.