Question

I would like to read some data from a stream I have using std::getline.
Below a sample using the std::cin.

std::string line;
std::getline( std::cin, line );

This is a blocking function i.e. if there is no data or line to read it blocks execution.

Do you know if exists a function for checking data availability before calling std::getline? I don’t want to block.

How can I check whether the stream buffer is full of data valid for a successful call to std::getline?

Whatever looks like the code below

if( dataAvailableInStream() )
{
     std::string line;
     std::getline( std::cin, line );
}

Answer 1

The iostream library doesn’t support the concept of non-blocking I/O. I don’t think there’s anything in the C++ standard that does. Any good solution would likely be platform-specific. If you can use the POSIX libraries, you might look into select. It’s usually used for networking stuff, but it’ll work just fine if you pass it the file descriptor for stdin.