java - 从 Java 程序运行系统命令时无输出

Question

这是尝试运行系统命令的代码:

String command = "java -cp 1outinstr;out Main";
Process p      = Runtime.getRuntime().exec("cmd /c " + command);

我的问题是我看不到命令​​的输出。

Answer 1

该命令运行正常，只是未连接到控制台。

如果您想查看命令的输出，您必须自己打印它:

String command = "java -cp 1outinstr;out Main";
Process p = Runtime.getRuntime().exec("cmd /c " + command);

BufferedReader stdInput = new BufferedReader(new InputStreamReader(
        p.getInputStream()));

BufferedReader stdError = new BufferedReader(new InputStreamReader(
        p.getErrorStream()));

// read the output from the command
System.out.println("Here is the standard output of the command:\n");
String s = null;
while ((s = stdInput.readLine()) != null) {
    System.out.println(s);
}

// read any errors from the attempted command
System.out
        .println("Here is the standard error of the command (if any):\n");
while ((s = stdError.readLine()) != null) {
    System.out.println(s);
}

code taken from another answer

如果您想了解更多信息，请阅读 standard streams :

In computer programming, standard streams are preconnected input and output channels between a computer program and its environment (typically a text terminal) when it begins execution. The three I/O connections are called standard input (stdin), standard output (stdout) and standard error (stderr). - from Wikipedia