7 replies to this topic

[alirezan]

Hi
I am trying to find a way to convert from char * to string.
I have:

char * buf = "test";

and I want to look for a substring in this. I tried using strcpy:

string s;
strcpy (s, buf);

but it keeps telling me: "No instance of function "strcpy" matches the argument list.

Anybody knows a way of doing this?

Thanks

[mebob]

IDK about that error, but first I must tell you, strcpy is NOT compatible with C++ strings. If you want to convert from char * to string, you would do something like this:

char *but = "test";
string s;
s = buf;

If you want to use strcpy, however, for copying one C string to another, you must make sure you have the library included:

#include <cstring> //For C++
#include <string.h> //For C

BTW, use the code tags for you code. In the editor, it is the # symbol.

[ZekeDragon]

You can simply use the (overloaded) assignment operator to assign a char * to a std::string. This will copy all the data over automatically.

If you're trying to copy from a std::string to a char *, the best way to do that is with strncpy(), but you have to get the char data from the string first!

size_t my_str_size_with_null_end = my_str->size() + 1;
  char *buffer = malloc(my_str_size_with_null_end);
  strncpy(buffer, my_str->c_str(), my_str_size_with_null_end);

[RhetoricalRuvim]

...

char *but = "test";
string s;
s = buf;

...

In 'char * but= "test";' , I suppose you meant 'char * buf= "test";' .

...In the editor, it is the # symbol.

This editor? I thought it was [CODE] and [/CODE] that make code tags.

[ZekeDragon]

@RhetoricalRuvim: Both of them work. I prefer [noparse][code=auto:0][/noparse] tags myself, along with any other tags I can use. The only real trouble I have with the quick reply window here is that it keeps the formatting of pasted text, which forces me to put it through a text editor first.

[mebob]

LOL typo, sorry.

[Flying Dutchman]

No one really mentioned the std::string ctor:

char* buf = "test";
std::string s(buf);

[Biofag]

don't forget the size, if you don't specify the buf size in the constructor, you could read garbage:

std::string s(buf, buf_size);

I'd use this, i had problems reading input files in a game and that was the cause