Question

I want to convert a std::string into a char* or char[] data type.

std::string str = "string";
char* chr = str;

Results in: “error: cannot convert ‘std::string’ to ‘char’ …”.

What methods are there available to do this?

Answer 1

It won’t automatically convert (thank god). You’ll have to use the method c_str() to get the C string version.

std::string str = "string";
const char *cstr = str.c_str();

.c_str() returns a const char *. If you want a non-const char *, use .data():

std::string str = "string";
char *cstr = str.data();

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Some other options:

• Copying the characters into a vector:

  std::vector<char> cstr(str.c_str(), str.c_str() + str.size() + 1);
  

  Then cstr.data() will give you the pointer.

  This version copies the terminating \0. If you don’t want it, remove + 1 or do std::vector<char> cstr(str.begin(), str.end());.

• Copying into a manually allocated array: (should normally be avoided, as manual memory management is easy to get wrong)

  std::string str = "string";
  char *cstr = new char[str.size() + 1];
  std::strcpy(cstr, str.c_str());
  // do stuff
  delete [] cstr;