But I made a expirementation and found that "^cde" couldn't neither match "cdefg", nor "abcde",
^cde will *find* a match in cdefg if you call regex_search, it will not succeed if you call regex_match however as that requires *all* of the string to be matched. "abcde" will never be matched by ^cde.
Anchors:
A '^' character shall match the start of a line.
A '$' character shall match the end of a line. I still can't understand it exactly, if "^cde$" only matches "cde", why we need to write the regex as "^ced$"?
What? ^cde$ will match the characters "cde" *only* if: 1) The "c" was preceeded by a line break character, or the "c" was the first character in the string. *and* 2) The "e" character is followed by a line break character or is the last character in the string. So using regex_search the following strings contain matches for ^cde$ : cde \ncde \ncde\n cde\n However, using regex_match only the first of those strings would be matched. John.