java - Java 中的 Linux 命令 "write all used jars by JVM to file"

Question

我想知道所有不同运行的 JVM 加载了哪些 jar。

如果我输入 “lsof -p $PID | grep jar >>/somefile” 从 bash/命令，它工作得很漂亮! (用实际进程 ID 替换 $PID)。但是，我希望能够从 Java 程序中执行此操作。 我希望下面的代码可以工作，但没有文件被写入:

public static void printCustomCommand(){
    String[] pids = {"pidof java"};
    String s;

    try {
        Process pidProcess = Runtime.getRuntime().exec("pidof java");
        BufferedReader br = new BufferedReader(new InputStreamReader(pidProcess.getInputStream()));
        pids = br.readLine().split(" ");

        for (String pid : pids){
            String cmd = "lsof -p " + pid + " | grep jar >> /somepath/mydumpfile";
            Process p;
            p = Runtime.getRuntime().exec(cmd);
            System.out.println(p.waitFor());
        }

        //pids = new String(bo).split(" ");
    } catch (IOException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

当我打印 p.waitFor() 命令时，它总是返回 1，这意味着根据 API 文档“有些东西不正确”。 http://docs.oracle.com/javase/6/docs/api/java/lang/Process.html#waitFor%28%29

Answer 1

问题是 Runtime.exec() 不理解“|”等 shell 概念。 试试这个:

public static void printCustomCommand(){
    String[] pids = {"pidof java"};
    String s;

try {
    Process pidProcess = Runtime.getRuntime().exec("/bin/bash -c pidof java");
    BufferedReader br = new BufferedReader(new InputStreamReader(pidProcess.getInputStream()));
    pids = br.readLine().split(" ");

    for (String pid : pids){
        String cmd = "/bin/bash -c lsof -p " + pid + " | grep jar >> /somepath/mydumpfile";
        Process p;
        p = Runtime.getRuntime().exec(cmd);
        BufferedReader reader = 
        new BufferedReader(new InputStreamReader(p.getInputStream()));

    String line = "";
    while((line = reader.readLine()) != null) {
        System.out.print(line + "\n");
    }

    p.waitFor();  
    }

    //pids = new String(bo).split(" ");
} catch (IOException e1) {
    // TODO Auto-generated catch block
    e1.printStackTrace();
} catch (InterruptedException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}
}

问题是 exec 直接运行二进制文件而不调用 shell。 “|”字符只能被 shell 识别。 “-c”告诉 shell 运行单个命令，并将整个命令作为单个参数传递。