CODEWITHSUNDEEP
c++stringcopy
Muhammad Arslan Jamshaid
Muhammad Arslan Jamshaid

Reputation: 1193

How to copy a string of std::string type in C++?

I used the strcpy() function and it only works if I use C-string arrays like:

char a[6] = "text";
char b[6] = "image";
strcpy(a,b);

but whenever I use

string a = "text";
string b = "image";
strcpy(a,b);

I get this error:

functions.cpp: no matching function for call to strcpy(std::string&, std::string&)

How to copy 2 strings of string data type in C++?

Upvotes: 68

Views: 225466

Answers (4)

user2133061
user2133061

Reputation:

Caesar's solution is the best in my opinion, but if you still insist to use the strcpy function, then after you have your strings ready:

string a = "text";
string b = "image";

You can try either:

strcpy(a.data(), b.data());

or

strcpy(a.c_str(), b.c_str());

Just call either the data() or c_str() member functions of the std::string class, to get the char* pointer of the string object.

The strcpy() function doesn't have overload to accept two std::string objects as parameters. It has only one overload to accept two char* pointers as parameters.

Both data and c_str return what does strcpy() want exactly.

Upvotes: 4

Caesar
Caesar

Reputation: 9863

You shouldn't use strcpy() to copy a std::string, only use it for C-Style strings.

If you want to copy a to b then just use the = operator.

string a = "text";
string b = "image";
b = a;

Upvotes: 97

bames53
bames53

Reputation: 88225

strcpy is only for C strings. For std::string you copy it like any C++ object.

std::string a = "text";
std::string b = a; // copy a into b

If you want to concatenate strings you can use the + operator:

std::string a = "text";
std::string b = "image";
a = a + b; // or a += b;

You can even do many at once:

std::string c = a + " " + b + "hello";

Although "hello" + " world" doesn't work as you might expect. You need an explicit std::string to be in there: std::string("Hello") + "world"

Upvotes: 22

th3an0maly
th3an0maly

Reputation: 3510

strcpy example:

#include <stdio.h>
#include <string.h>

int main ()
{
  char str1[]="Sample string" ;
  char str2[40] ;
  strcpy (str2,str1) ;
  printf ("str1: %s\n",str1) ;
  return 0 ;
}

Output: str1: Sample string

Your case:

A simple = operator should do the job.

string str1="Sample string" ;
string str2 = str1 ;

Upvotes: 4

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