Replace double slashes to four slashes

Question

I have char data type that contain a directory with double slashes. I want to replace the double slashes to four slashes so that my output will be double slashes. I had tried a lots of solutions, but nothing works.

char *str = "C:\\Users\\user\\desktop";
for(int i = 0;i < strlen(str) ; i++)
    if(str[i] == '\\')  
    str[i] =='\\\\'; 

The output of this code shows 'C:\Users\user\desktop'.

Answer 1

First off, since you're using c++, consider using std::string. Modifying a string literal is undefined behavior (either copy the string literal into a buffer, or use a char [] or std::string in the first place.)

Second, string literals must be enclosed in double quotes.

Third, you require two sets of backslashes for every backslash you escape. \\\\ turns into \\.

---

This should do the trick:

std::string s("C:\\Users\\user\\desktop");
auto it = std::find(s.begin(), s.end(), '\\');
while (it != s.end()) {
    auto it2 = s.insert(it, '\\');

    // skip over the slashes we just inserted
    it = std::find(it2+2, s.end(), '\\');
}
std::cout << s; // C:\\Users\\user\\desktop

Answer 2

So the first sentence is incorrect -- you do not have a directory with double slashes. The \\ in the string literal represents just a single character in the actual string.

If you do want to do this, a single replacement won't work, as that will overwrite your next character. You'll have to build a whole new string, moving one character at a time (and occasionally writing an extra character to the output).

However, I suspect that's a really big If in that previous sentence. Are you sure that you actually need doubled slashes? There may be a reason for it, but I can't think of one off the top of my head.