How to append a string to a argv

Question

I want to remove a file, the name of which is given as an argument to the program; but, as the filetype will remain constant (.bat), I want it to be automatically given by the program (e.g. running deletefile.exe script will delete "script.bat" (which is in the same directory)). I have seen this question, but the solution does not seem to work.

Have I misinterpreted something here?

My attempt is below:

#include <iostream>
#include <fstream>
#include <string>


using namespace std;

int main(int argc, char *argv[]){

    if(argv[1] == string("del")){
        string file_to_remove;
        file_to_remove = argv[2]+".bat";
        if (remove(file_to_remove.c_str()) != 0){
            cout<<"Error in file deletion.\n";
        }
        else {
            cout<<"Removed alias " << argv[2] << "\n";
        }
    }
    return 0;
}

But this results in a compiler error

<source>: In function 'int main(int, char**)':
<source>:12:33: error: invalid operands of types 'char*' and 'const char [5]' to binary 'operator+'
   12 |         file_to_remove = argv[2]+".bat";
      |                          ~~~~~~~^~~~~~~
      |                                | |
      |                                | const char [5]
      |                                char*

Answer 1

The right-hand side of your file_to_remove = argv[2]+".bat"; statement is attempting to concatenate two char* strings using the + operator; you can't do this, and at least one of the operands must be made into a std::string.

You can do this by constructing a temporary std:string, like this:

file_to_remove = string(argv[2]) + ".bat";

Or, more tersely (since C++14), by adding the s suffix to the string literal:

file_to_remove = argv[2] + ".bat"s;