How can I copy multiple char* strings into one using strcpy_s()?

Question

Using the strcpy_s() function I want to collate the first three strings into the final one to print my full name. This is what I have and it doesn't work as I'm using char* strings and not std::string s.

#include <iostream>
using namespace std;

int main()
{
    char str_first[] = "Nerf_";
    char str_middle[] = " Herder";
    char str_last[] = "42";

    char str_fullName[35];

    strcpy_s(str_fullName, (str_first + str_middle + str_last).c_str());
    cout << str_fullName;
}

Any suggestions?

Answer 1

This should be close to what you're looking for, strictly using strcpy_s to concatenate strings together:

#include <string.h>
#include <iostream>
using namespace std;

int main()
{
    char str_first[] = "Nerf_";
    char str_middle[] = " Herder";
    char str_last[] = "42";

    char str_fullName[35];

    int index = strcpy_s(str_fullName, sizeof str_fullName, str_first);
    index += strcpy_s(str_fullName + index, sizeof str_fullName - index, str_middle);
    index += strcpy_s(str_fullName + index, sizeof str_fullName - index, str_last);
    cout << str_fullName;
}

The index variable serves a couple of purposes: (1) to provide a new index into the output str_fullName string as the string is built, and (2) subtracted from sizeof str_fullName , it "adjusts" the available buffer size as the string is built.

Caveats are that you should add overflow checking via the output from strcpy_s , and (as noted by others) there are better patterns to follow for doing this, but probably as an academic exercise there's something good to be learned here.

Answer 2

You need to use both strcat and strcpy

See code comments for more info.

// disable SDL warnings in Visual studio
#define _CRT_SECURE_NO_WARNINGS

#include <cstring>
#include <iostream>
using namespace std;

int main()
{
    // TODO: insert checking code,
    // to make sure destination can hold all characters + one termination.

    char str_first[] = "Nerf_";
    char str_middle[] = " Herder";
    char str_last[] = "42";

    char str_fullName[35];

    // copy first string because we need null terminated destination
    strcpy(str_fullName, str_first);

    // append the rest, string is auto null terminated.
    strcat(str_fullName, str_middle);
    strcat(str_fullName, str_last);

    cout << str_fullName;
}

Answer 3

If I am not mistaken the function strcpy_s expects three arguments. So either supply one more argument to the function call or use instead the function strcpy .

And there is no need to use the standard class std::string to perform the task.

The code can look the following way

strcpy( str_fullName, str_first );
strcat( str_fullName, str_middle );
strcat( str_fullName, str_last );

Or you could use strcpy_s and strcat_s provided that you will specify the correct number of arguments.

Pay attention to that you need to include the header

#include <cstring>