coreutils: Charset selection in ptx
7.5.2 Charset selection
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As it is set up now, the program assumes that the input file is coded
using 8-bit ISO 8859-1 code, also known as Latin-1 character set,
_unless_ it is compiled for MS-DOS, in which case it uses the character
set of the IBM-PC. (GNU ‘ptx’ is not known to work on smaller MS-DOS
machines anymore.) Compared to 7-bit ASCII, the set of characters which
are letters is different; this alters the behavior of regular expression
matching. Thus, the default regular expression for a keyword allows
foreign or diacriticized letters. Keyword sorting, however, is still
crude; it obeys the underlying character set ordering quite blindly.
‘-f’
‘--ignore-case’
Fold lower case letters to upper case for sorting.