We saw how to match a set of characters using the character class, then we saw how to match a range of characters using character ranges.
Actually, the ERE engine offers ready-to-use classes to match some common sets of characters as follows:
| [[:alpha:]] |
Matches any alphabetical character |
| [[:upper:]] |
Matches A–Z uppercase only |
| [[:lower:]] |
Matches a–z lowercase only |
| [[:alnum:]] |
Matches 0–9, A–Z, or a–z |
| [[:blank:]] |
Matches space or Tab only |
| [[:space:]] |
Matches any whitespace character: space, Tab, CR |
| [[:digit:]] |
Matches from 0 to 9 |
| [[:print:]] |
Matches any printable character |
| [[:punct:]] |
Matches any punctuation character |
So, if you want to match uppercase characters, ...
