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15.4. Determining Terminal or Window Size


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.


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

use Term::ReadKey;

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


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; Recipe 12.14