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Perl Cookbook
book

Perl Cookbook

by Tom Christiansen, Nathan Torkington
August 1998
Intermediate to advanced content levelIntermediate to advanced
800 pages
39h 20m
English
O'Reilly Media, Inc.
Content preview from Perl Cookbook

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; Section 15.6

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Publisher Resources

ISBN: 1565922433Supplemental ContentCatalog PageErrata