c++11/regex - search for exact string, escape
c++, c++11, regex, string
Solution
You will have to escape all special characters in the string with `\`. The most straightforward approach would be to use another expression to sanitize the input string before creating the expression `regex`.
// matches any characters that need to be escaped in RegEx
std::regex specialChars { R"([-[\]{}()*+?.,\^$|#\s])" };
std::string input = ">> "+ s1 +" <<";
std::string sanitized = std::regex_replace( input, specialChars, R"(\$&)" );
// "sanitized" can now safely be used in another expression
Problem
Say you have a string which is provided by the user. It can contain any kind of character. Examples are: ``` std::string s1{"hello world"); std::string s1{".*"); std::string s1{"*{}97(}{.}}\\testing___just a --%#$%# literal%$#%^"}; ... ``` Now I want to search in some text for occurrences of `>>` followed by the input string `s1` followed by `<<`. For this, I have the following code: ``` std::string input; // the input text std::regex regex{">> " + s1 + " <<"}; if (std::regex_match(input, regex)) { // add logic here } ``` This works fine if `s1` did not contain any special characters. However, if `s1` had some special characters, which are recognized by the regex engine, it doesn't work. How can I escape `s1` such that `std::regex` considers it as a literal, and therefore does not interpret `s1`? In other words, the regex should be: ``` std::regex regex{">> " + ESCAPE(s1) + " <<"}; ``` Is there a function like `ESCAPE()` in `std`? important I simplified my question. In my real case, the regex is much more complex. As I am only having troubles with the fact the `s1` is interpreted, I left these details out.