Q:

How can I print out the iskeyword characters?

When I use :set iskeyword? to view keyword characters, result for shell scripts is:
iskeyword=@,48-57,_,192-255,-

:h iskeyword says @ expands to any alpha character that the isalpha() functions returns true on, but what about 48-57 and 192-255 how can I view these characters?

A:

You can use:
:echo map(range(48, 57), 'nr2char(v:val)')
:echo map(range(192, 255), 'nr2char(v:val)')

Which should output:

['0', '1', '2', '3', '4', '5', '6', '7', '8', '9']
['À', 'Á', 'Â', 'Ã', 'Ä', 'Å', 'Æ', 'Ç', 'È', 'É', 'Ê', 'Ë', 'Ì', 'Í', 'Î', 'Ï', 'Ð', 'Ñ', 'Ò',
  'Ó', 'Ô', 'Õ', 'Ö', '×', 'Ø', 'Ù', 'Ú', 'Û', 'Ü', 'Ý', 'Þ', 'ß', 'à', 'á', 'â', 'ã', 'ä', 'å', '
  æ', 'ç', 'è', 'é', 'ê', 'ë', 'ì', 'í', 'î', 'ï', 'ð', 'ñ', 'ò', 'ó', 'ô', 'õ', 'ö', '÷', 'ø', 'ù
  ', 'ú', 'û', 'ü', 'ý', 'þ', 'ÿ']

To break it down:

range(192, 255) makes a list from 192 to 255.
nr2char() converts a number from its ASCII code to a string.
map() applies nr2char() to every item in the list.

