Dealing with char ** argv

Question

How do I assign a sequence of character strings to a char ** argv variable in a program? Its a command line argument. I'm currently trying to convert an .exe app to a dll.

For example:

{ "string1", "string2", "string3" } --- > char ** argv variable

My problem is somehow realted to this: http://stackoverflow.com/questions/1015944/how-does-an-array-of-pointers-to-pointers-work/1015970#1015970 but I can't get it to work using the snippet shown there. Help!

Answer 1

const char* argv[] = {"string1", "string2", "string3", 0};

If the arguments aren't compile time constants I would do something like:

std::vector<const char*> arguments;
arguments.push_back(somePointer);
arguments.push_back(someOtherPointer);
arguments.push_back(0);
const char** argv = &arguments[0];

EDIT: Using PaxDiablos information that an argv-array should be null terminated.

Answer 2

I can't use vectors. Any other answers?

Answer 3

what about getopt?

Answer 4

Note that Andreas Brincks answer is really what you want to do, where vector does all the heavy lifting of allocation and provides exception safety. I strongly suggest that you look into changing whatever reason there is for not being able to use vector. But if you really really cannot do so, I guess you could do something along the lines of the below code:

int numArgs = YOUR_NUMBER_HERE;

char **myArgv = new char*[numArgs+1];

for (int i=0; i<numArgs; ++i) {
    myArgv[i] = new char[at least size of your argument + 1];
    strncpy(myArgv[i], whereever your string is, buffer size);
    myArgv[buffer size] = '\0';
}
myArgv[numArgs] = NULL;


// use myArgv here


// now you need to manually free the allocated memory
for (int i=0; i<numArgs; ++i) {
    delete [] myArgv[i];
}
delete [] myArgv;