Runtime.getRuntime（）。exec（）不执行某些命令

Question

I'm beginner at java and have some problems. I've read several topics about this theme but none of them worked for me. Here is my code:

try 
{

        Console console = System.console();

        String command;

        while(true)
        {
            command = console.readLine("Enter input:");
            Process proc = Runtime.getRuntime().exec(command);

            // Read the output

            BufferedReader reader =  
                  new BufferedReader(new InputStreamReader(proc.getInputStream()));

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

            proc.waitFor(); 
        }



}
    catch(Exception e) {} 

So what I'm trying is to make a java program and run terminal commands in it(I'm using linux). This program works with commands like "ls" "ps ef" and others but it doesn't work when I type "cd". I know that cd makes different process and should be used this way: "Runtime.exec(String command, String[] envp, File dir)". My questions is:
How to make my program run all kinds of terminal commands? Sorry if question sound silly. Thank you.

Answer 1

您实际上必须运行要使用的控制台（例如，sh，csh，bash等），然后使用进程OutputStream来输入命令

Answer 2

I think the Problem is not your Code, the command is the problem...

what do you want to see if your command is cd ??

In Background it changes the path but you get nothing back.

Changing the Directory is not processing any output.

Answer 3

The cd command is a shell built-in command. There is no shell when you run a command via exec(...) . Indeed, if you try to find a cd command in any of your system's bin directories, you won't find one ... because it is impossible to implement as a regular command.

If you are trying to use cd to change the current directory for the JVM itself, that won't work because a command can only change the current directory of itself and (after that) commands that it launches itself. It can't change its parent processes current directory.

If you are trying to use cd to change the current directory for subsequent commands, that won't work either. The context in which you set the current directory ends when the command finishes.

In fact, the right way to change the directory for a command run using exec is to set it via the ProcessBuilder API itself.

---

How to make my program run all kinds of terminal commands?

You can't. Some of the "terminal commands" only make sense as shell commands, and that means you need a shell.

I suppose, you could consider emulating the required behaviour in your Java code. That would work for cd ... but other commands are likely to be more difficult to cope with.

(For what it is worth, it is possible to implement a POSIX compatible shell in Java. It is just a LOT of work.)

Answer 4

这对我有用：

Runtime.getRuntime().exec(new String[]{ "/system/bin/sh", "-c", "ls -l" } );