Perl Cookbook

Determining Terminal or Window Size

Problem

You need to know the size of the terminal or window. For instance, you want to format text so that it doesn’t pass the right-hand boundary of the screen.

Solution

Either use the ioctl described in Section 12.14, or else use the CPAN module Term::ReadKey:

use Term::ReadKey;

($wchar, $hchar, $wpixels, $hpixels) = GetTerminalSize();

Discussion

GetTerminalSize returns four elements: the width and height in characters and the width and height in pixels. If the operation is unsupported for the output device (for instance, if output has been redirected to a file), it returns an empty list.

Here’s how you’d graph the contents of @values, assuming no value is less than 0:

use Term::ReadKey;

($width) = GetTerminalSize();
die "You must have at least 10 characters" unless $width >= 10;

$max = 0;
foreach (@values) {
    $max = $_ if $max < $_;
}

$ratio = ($width-10)/$max;          # chars per unit
foreach (@values) {
    printf("%8.1f %s\n", $_, "*" x ($ratio*$_));
}

See Also

The documentation for the Term::ReadKey module from CPAN; Section 12.14