C++ :: Using File From Command Line

I'm trying to read in a file specified in the command line but I'm having some trouble. The command line entry specifies the inputfile preceded by '<' and the output file preceded by '>' like so

./program -v < input_file.cmd > output_file.cmd

This is what I've got so far.

int main(int argc,char* argv[]){
string strv="-v";
string input="<";
string output=">";
string str;
string input_file;
const char* in=input_file.c_str();

[Code] .....

This compiles ok, but when i run it using :

./program -v < test1.cmd

I get a segfault, if i cout argc it returns '2' where i would expect for this command line entry, I 'd get 4.

I'm not yet outputting to file, just to the screen so im not specifying an output file yet.