从java代码获取cmd命令的输出
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Get output of cmd command from java code
提问by hakuna matata
I have a program where I was able to successfully execute cmd commands from my code, but I want to be able to get the output from the cmd command. How can I do that?
我有一个程序，可以从我的代码中成功执行 cmd 命令，但我希望能够从 cmd 命令中获取输出。我怎样才能做到这一点？
So far my code is:
到目前为止，我的代码是：
Second.java:
二.java：
public class Second {
public static void main(String[] args) {
System.out.println("Hello world from Second.java");
}
}
and Main.java
和 Main.java
public class Main {
public static void main(String[] args) {
String filename = args[1].substring(0, args[1].length() - 5);
String cmd1 = "javac " + args[1];
String cmd2 = "java " + filename;
Runtime r = Runtime.getRuntime();
Process p = r.exec(cmd1); // i can verify this by being able to see Second.class and running it successfully
p = r.exec(cmd2); // i need to see this output to see if
System.out.println("Done");
}
}
I can check the first command is working successfully by checking for Second.class, but what if this class generated some error, how will I be able to see that error?
我可以通过检查 Second.class 来检查第一个命令是否成功运行，但是如果这个类产生了一些错误，我怎么能看到那个错误呢？
采纳答案by Elliott Frisch
You need to the OutputStream (InputStream) of your Process (and you should use a ProcessBuilder)... like so
你需要你的进程的输出流（输入流）（你应该使用一个 ProcessBuilder）......像这样
public static void main(String[] args) {
String filename = args[1].substring(0, args[1].length() - 5);
String cmd1 = "javac " + args[1];
String cmd2 = "java " + filename;
try {
// Use a ProcessBuilder
ProcessBuilder pb = new ProcessBuilder(cmd1);
Process p = pb.start();
InputStream is = p.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(is));
String line = null;
while ((line = br.readLine()) != null) {
System.out.println(line);
}
int r = p.waitFor(); // Let the process finish.
if (r == 0) { // No error
// run cmd2.
}
} catch (Exception e) {
e.printStackTrace();
}
}
回答by T McKeown
look here: Extracting a process's exit code in the case of ThreadInterrupted
看这里： 在 ThreadInterrupted 的情况下提取进程的退出代码
You need to get the return code... you must wait for it.
你需要得到返回码……你必须等待它。
回答by Paul Lo
A general example to get the return from a command would be:
从命令中获取返回的一般示例是：
Process p = null;
try {
p = p = r.exec(cmd2);
p.getOutputStream().close(); // close stdin of child
InputStream processStdOutput = p.getInputStream();
Reader r = new InputStreamReader(processStdOutput);
BufferedReader br = new BufferedReader(r);
String line;
while ((line = br.readLine()) != null) {
//System.out.println(line); // the output is here
}
p.waitFor();
}
catch (InterruptedException e) {
...
}
catch (IOException e){
...
}
finally{
if (p != null)
p.destroy();
}
