Checking for Waiting Input

Problem

You want to know whether keyboard input is waiting without actually reading it.

Solution

Use the CPAN module Term::ReadKey, and try to read a key in non-blocking mode by passing it an argument of -1:

use Term::ReadKey; ReadMode ('cbreak'); if (defined ($char = ReadKey(-1)) ) {
 # input was waiting and it was $char
}
else {
 # no input was waiting
}
ReadMode ('normal'); # restore normal tty settings

Discussion

The -1 parameter to ReadKey indicates a non-blocking read of a character. If no character is available, ReadKey returns undef.

See Also

The documentation for the Term::ReadKey module from CPAN;