‘\cC’
matches any character whose category is C. Here C is a character
that represents a category: thus, ‘c’ for Chinese characters or ‘g’
for Greek characters in the standard category table. You can see
the list of all the currently defined categories with ‘M-x
describe-categories <RET>’. You can also define your own
categories in addition to the standard ones using the
‘define-category’ function (*note Categories::).
‘[ ... ]’
is a “character alternative”, which begins with ‘[’ and is
terminated by ‘]’. In the simplest case, the characters between
the two brackets are what this character alternative can match.
Thus, ‘[ad]’ matches either one ‘a’ or one ‘d’, and ‘[ad]*’ matches
any string composed of just ‘a’s and ‘d’s (including the empty
string). It follows that ‘c[ad]*r’ matches ‘cr’, ‘car’, ‘cdr’,
‘caddaar’, etc.
Example:
ht 删掉 t 我 p 删掉 s 我: 删我 / 删我 /w 删我 w 删我 w 删我. 删我 ex 删我 am 删我 ple 删我 . 删我 co 删掉 m 我 / 删我 i7 删我 mx 删我 ss 删我 d
M-x isearch-forward-regexp RET \(\cc\| \)
then replace it with empty string gives the result of
`https://www.example.com/i7mxssd`
but I wonder how to use \cc inside [] instead of \(\cc\| \)