String to C String

[APwrs]

I was wondering, how do I convert (or copy) a std::string to an old-style C string? Thank you.

[vhg119]

cant you just assing a string object to a char pointer?
like
string a = "hello";
char* b;

b = a;

? no?

doesnt a string object have a overloaded assigment operator?

[APwrs]

That doesn't quite work. Doing that kicks out the following error message:

Sfe.cpp: In function `int main(int, char**)':
Sfe.cpp:12: cannot convert `std::string' to `char*' in assignment

Thanks for trying, though.

[infidel]

Greetings,

std::string has a 'c_str()' member function that returns a const char* pointer to the string. If you just need to call a function that takes a const char* parameter you can do it like:

#include <string>

void function_that_takes_a_c_string(const char* string);

int main(int argc, char** argv)
{
std::string str("The rain in Spain stays mainly in the plane");
fucntion__that_takes_a_c_string(str.c_str());
}

void function_that_takes_a_c_string(const char* string)
{
// If the function needs to modify the string it should copy it first
// because it is a const char*.
// Note that the changes to the copied string will not be reflected
// int the original one!
char c_string = new char[strlen(string)];
strncpy(c_string, string, strlen(string)];
...
...
}

I'd stay away from C string as much as I can, and use the std::string member functions and operators where possible, it's much safer, cleaner code and sexier! :D
Anyway, when necessary you can convert it to a C string like I've shown above.

Hope this helps.

[vhg119]

does anyone know of a good c++ reference book?
i cant seem to find a c++ in a nutshell anywhere

[busa_blade]

use the function

c_str()
method

I use the C/C++ Programmer's Reference by Herbert Schlidt

It's a pretty good reference

[APwrs]

Thank you very much infidel, that was exactly what I needed. I agree with you that it's best to stay way from C strings, but I needed the conversion because I needed to pass a std::string to a system() call, which only takes C strings. I also would like to thank everyone else that replied for their help as well, it is always greatly appreciated.