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3.10. Short Sleeps


You need to sleep for less than a second.


Use the select() function, if your system supports it:

select(undef, undef, undef, $time_to_sleep);

Some systems don't support a four-argument select . The Time::HiRes module provides a sleep function that takes a floating point number of seconds:

use Time::HiRes qw(sleep);


Here's an example of select . It's a simpler version of the program in Recipe 1.5 . Think of it as your very own 300-baud terminal.

while (<>) {
    select(undef, undef, undef, 0.25);

Using Time::HiRes, we'd write it as:

use Time::HiRes qw(sleep);
while (<>) {

See Also

The documentation for the CPAN modules Time::HiRes and BenchMark; the sleep and select functions in perlfunc (1) and Chapter 3 of Programming Perl ; we use the select function for short sleeps in the slowcat program in Recipe 1.5

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