The match_results::length() is a inbuilt function in C++ which is used to return the length of a particular match in the match_results object.
smatch_name.length(n) Note: smatch_name is an object of match_results class.
Parameters: It accepts a single parameter n which specifies the Match number. It is lower than match_results::size. The match number 0 represents the entire matched expression. Subsequent match numbers identify the sub-expressions if any. The passed integral is an unsigned integral type.
Return Value:It returns the length of the n-th match in the match_results object.
Note: First element always contains the whole regex match while the others conatain the particular Capturing Group.
Below programs illustrate the above function.
match 0 has a length of 13 match 1 has a length of 5 match 2 has a length of 8
max-length sub match is forgeeks with a length of 8