> but they mean “any character between the character ‘a’ and the character ‘z’”, which happens to correspond to the lower case letters in English ‘Only’ in the

> but they mean “any character between the character ‘a’ and the character ‘z’”, which happens to correspond to the lower case letters in English ‘Only’ in the most commonly used character encodings. In EBCDIC (https://en.wikipedia.org/wiki/EBCDIC https://en.wikipedia.org/wiki/EBCDIC), the [a-z] range includes more than 26 characters. That’s one of the reasons POSIX has character classes (https://en.wikipedia.org/wiki/Regular_expression#Character_classes https://en.wikipedia.org/wiki/Regular_expression#Character_c...). [:lower:] always gets you the lowercase characters in the encoding that the program uses.