I have a console app in which I want to give the user x seconds to respond to the prompt. If no input is made after a certain period of time, program logic should continue. We assume a timeout means empty response.
What is the most straightforward way of approaching this?
I'm surprised to learn that after 5 years, all of the answers still suffer from one or more of the following problems:
I believe my solution will solve the original problem without suffering from any of the above problems:
class Reader {
private static Thread inputThread;
private static AutoResetEvent getInput, gotInput;
private static string input;
static Reader() {
getInput = new AutoResetEvent(false);
gotInput = new AutoResetEvent(false);
inputThread = new Thread(reader);
inputThread.IsBackground = true;
inputThread.Start();
}
private static void reader() {
while (true) {
getInput.WaitOne();
input = Console.ReadLine();
gotInput.Set();
}
}
// omit the parameter to read a line without a timeout
public static string ReadLine(int timeOutMillisecs = Timeout.Infinite) {
getInput.Set();
bool success = gotInput.WaitOne(timeOutMillisecs);
if (success)
return input;
else
throw new TimeoutException("User did not provide input within the timelimit.");
}
}
Calling is, of course, very easy:
try {
Console.WriteLine("Please enter your name within the next 5 seconds.");
string name = Reader.ReadLine(5000);
Console.WriteLine("Hello, {0}!", name);
} catch (TimeoutException) {
Console.WriteLine("Sorry, you waited too long.");
}
Alternatively, you can use the TryXX(out)
convention, as shmueli suggested:
public static bool TryReadLine(out string line, int timeOutMillisecs = Timeout.Infinite) {
getInput.Set();
bool success = gotInput.WaitOne(timeOutMillisecs);
if (success)
line = input;
else
line = null;
return success;
}
Which is called as follows:
Console.WriteLine("Please enter your name within the next 5 seconds.");
string name;
bool success = Reader.TryReadLine(out name, 5000);
if (!success)
Console.WriteLine("Sorry, you waited too long.");
else
Console.WriteLine("Hello, {0}!", name);
In both cases, you cannot mix calls to Reader
with normal Console.ReadLine
calls: if the Reader
times out, there will be a hanging ReadLine
call. Instead, if you want to have a normal (non-timed) ReadLine
call, just use the Reader
and omit the timeout, so that it defaults to an infinite timeout.
So how about those problems of the other solutions I mentioned?
The only problem that I foresee with this solution is that it is not thread-safe. However, multiple threads can't really ask the user for input at the same time, so synchronization should be happening before making a call to Reader.ReadLine
anyway.