How to convert std::string to const char in C++

Question

I tried to research this for a bit and I can't figure out the problem

Here's the code:

#include <iostream>
#include <stdlib.h>
#include <string>
void choose();
void newuser();
void admuse();

using namespace std;
string x;
string z;
string w;

void CreNeAcc(){


cout << "Enter User Name for your new account\n";
getline(cin, x);

cout << "Enter Password for your new account\n";
getline(cin, z);

cout << "Would you like the account to be admin?\n";
cout << "Yes = Y, No = N\n";
getline(cin, w);
choose();

}

void choose(){

if(w == "Y"){
newuser();
admuse();
}else if(w == "N"){
newuser();
}else{
cout << "Invalide Command\n";
}

}



void newuser(){

const char* Letter_x = x.c_str();
char command [100] = "net user /add ";
strcat(command, x); //This is where I get the error
strcat(command, " ");
strcat(commad, z);
system(command);
}

void admuse(){
    system("new localgroup administrators " << x << " /add")
}

also the error its giving me is:

cannot convert 'std::string {aka std::basic_string<char>}' to 'const char*' for argument '2' to 'char* strcat(char*, const char*)'|

You already have the answer in your question... – chris Dec 05 '13 at 02:04 — chris, Dec 05 '13 at 02:04

score 7 · Answer 1 · answered Dec 05 '13 at 02:21

You have to use c_str() (see here). It's implemented by simply apending it to your std::string, like so:

string myFavFruit = "Pineapple"
const char* foo = myFavFruit.c_str();
strcat(command, foo);

Actually, you have everything there you're just not using your const char* variable in the strcat()'s arguments. You define Letter_x, but then use x in the function instead. Rewrite your newuser() as follows:

void newuser(){

const char* Letter_x = x.c_str();
char command [100] = "net user /add ";
strcat(command, Letter_x); //Here, use 'Letter_x' instead of 'x'
strcat(command, " ");
strcat(command, z); //You will also need to do your 'c_str()' conversion on z before you can use it here, otherwise you'll have the same error as before.
system(command);
}

Lastly, you can avoid all this because you can append strings simply using the += operator (see here). Try this:

string command = "net user /add ";
command += x;
command += " ";
command += z;

Paweł Stawarz · Answer 2 · 2013-12-05T02:06:17.670

5

In order to convert a string into an const char* use c_str().

On a side note tho: why are you using strcat in the first place? You can concatenate strings with the operator+.

string a = "try", b = " this";
string c = a+b; // "try this"

edited Dec 05 '13 at 02:06

answered Dec 05 '13 at 02:05

Paweł Stawarz

3,952
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2

I think it's `c_str()`, right? – nhgrif Dec 05 '13 at 02:05
Of course. I had to somehow not press "_". Thanks for pointing that out! – Paweł Stawarz Dec 05 '13 at 02:07

score 1 · Answer 3 · edited May 23 '17 at 12:01

1

You might be looking for this: How to convert a char* pointer into a C++ string?

According to the link, you may use c_str() to return a pointer to a null terminated char array version of your string.

edited May 23 '17 at 12:01

Community

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answered Dec 05 '13 at 02:10

PritishC

508
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How to convert std::string to const char in C++

3 Answers3