circular shift

I'm trying to write a function that will shift letters in a string a given number of spaces to the left, moving letters that fall off the end to the front. In main the user puts in a command 'Lx' where 'x' is the number of spaces to shift. My problem is that the loop I have set up to move through the steps of the shift doesn't seem to be iterating. At All. It just prints out the user input unchanged. Here's my code:

  void ShiftLeft (char user_string[], int length, char shiftL_string[], std::string command)
{
    string number; //string after first character is erased
    int offSet; //number chars converted via atoi

    command.erase(0); //erase 'l'
    offSet = atoi (command.c_str()); //convert number into int

    int i; //initiate i
    //loops the for loop the number of times in offSet
    while(i < offSet)
    {
        i++; //increment i

        //following code moves first character to the end of the string
        char tmp; //tempmrarily holds char being swapped
        tmp = user_string[0]; //make first character equal to tmp
        user_string[0] = user_string[length]; //make first character equal to last
        user_string[length] = tmp;//make last character equal to temp

        int x;//initiat x
        //loops through chars of user string. Shifts characters to the left
        for (x = 0; x < offSet; x++)
            {
                cout << "Lx For loop" << endl;
                //shifts chars in string to the left
                tmp = user_string[x]; //makes char x equal to tmp
                //makes char x equal to the next char in array
                user_string[x] = user_string[x+1];
                user_string[x+1] = tmp;
            }
                cout << user_string << endl;

    }
}

I'm trying to get offSet (the number of spaces to shift) by erasing the first letter in the command string, and converting the leftover number into a int using atoi, setting that to the variable int offSet. Then I'm trying to use offSet at the number of times the shift loop iterates.

giblit (3750)

offset = x % stringSize

Then if you are shifting left you would take the offset amount of characters from the front and move them to the end. If it was a shift to the right you would take the offset amount of characters from the end and move them to the front. Kind of like prepend/appending.

Here is one method that takes advantage of iterators.

// Example program
#include <iostream>
#include <string>

int main()
{
    std::string input = "";
    std::cout << "Please enter a string: ";
    std::getline(std::cin, input);
    
    std::size_t offset = 0u;
    std::cout << "Please enter an offset: ";
    std::cin >> offset;
    offset = offset % input.size();
    
    std::string outputShiftedLeft = std::string(input.begin() + offset, input.end()) + std::string(input.begin(), input.begin() + offset);
    std::string outputShiftedRight = std::string(input.end() - offset, input.end()) + std::string(input.begin(), input.end() - offset);
    
    std::cout << "Original: " << input << '\n';
    std::cout << "Shifted Left: " << outputShiftedLeft << '\n';
    std::cout << "Shifted Right: " << outputShiftedRight << std::endl;
    
    return 0;
}

Please enter a string: GIBLIT
Please enter an offset: 2
Original: GIBLIT
Shifted Left: BLITGI
Shifted Right: ITGIBL

Though you can easily achieve this without iterators.

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