Java命令提示符模拟器

Question

I'm trying to make a java program that commands through cmd.exe and prints their output. To do this, I'm using this code:

cmdLine = Runtime.getRuntime().exec("cmd.exe");
cmdLineOut = new BufferedReader(new InputStreamReader(cmdLine.getInputStream()));
cmdLineIn = new PrintWriter(cmdLine.getOutputStream());
// ...
cmdLineIn.println(command);
cmdLineIn.flush();
String s = null;
while ((s = cmdLineOut.readLine()) != null)
    System.out.println(s);

Although, when input is given, the output is never printed.

EDIT: Solved The cmdLineOut.readLine() doesn't return null when the input is empty, it freezes. Since readLine freezes at the end no other code is executed, I just put the printing of the readLine in a seperate thread.

If somebody wants to answer this better, go ahead.

Answer 1

You never actually execute the user's command, at least in the snippet you posted. Also, nearly all command prompt "commands" are actually just programs that are on the default program search path. You should probably just Runtime.getRuntime().exec(user_command) for each command. This means that you will have to set up the input and output streams like you have already done for each command. You are right to get input in a separate thread, since attempting to read input will block the current thread until there is actually input to read. However, some commands, even under UNIX or Linux systems, are "built-in" (like cd ), meaning that the command prompt (aka "shell") handles the commands internally. Your program will have to test the user input to see if they are calling a built-in, and specially handle calls to built-in commands. Your program should actually be portable to non-Windows computers. Of course, the user would use different commands ( cp instead of copy ), but the only part you would have to add would be handling for other OS' shells' lists of built-ins (or simply have your program implement a "cross-platform" set of built-ins - this is your shell program, you get to make the rules).