taking command line input in different ways - c++

Question

How can one take command line argument by not using below structure ?
int main ( int argc, char* argv ) {
}
My question is really : how can I take below input :
./executableProgramName inputX inputY inputZ inputT
in any function ?
in foo () {
// what should I write so that I can get same effect
}
Are there any other way for taking command line input ?

Answer 1

The method specified by the standard for getting command line arguments is the argc and argv parameters passed to the entry point function main. There's no other standard method.
Some platforms offer non-standard methods. For example, if you're on Windows you can use GetCommandLineW
Here's an example that uses some C++11 stuff too.
#include <ShellAPI.h> // for CommandLineToArgvW
#include <string>
#include <vector>
#include <codecvt>
#include <locale>
int main() {
#ifdef WIN32
LPWSTR *szArglist;
int argc;
szArglist = CommandLineToArgvW(GetCommandLineW(),&argc);
if(NULL==szArglist) {
std::cerr << "CommandLineToArgvW failed\n";
}
std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>,wchar_t> convert; // codecvt_utf8 or codecvt<char16_t,char,mbstate_t> should work (will work once the char16_t specialization of codecvt works)
vector<string> args;
for(int i=0;i<argc;++i) {
args.push_back(convert.to_bytes(szArglist[i]));
}
#endif //ifdef WIN32
}

Answer 2

Maybe the best way is to forward the handling of command line arguments into an object, or simply a function:
#include <vector>
#include <string>
void handle_commandline_args(const std::vector<std::string>& args){
...
}
int main(int argc, char* argv[]){
handle_commandline_args(std::vector<string>(argv[0], argv[0] + argc));
...
}

Answer 3

You can not arbitrarily get the command-line arguments from any function. In C++, the only way command-line arguments are passed in is through the char* array in the main function.
If you want them to be accessible from anywhere, consider keeping them in a global variable, or passing them into each necessary function call. For example:
int argumentCount;
char **argumentArray;
int main ( int argc, char** argv )
{
argumentCount = argc;
argumentArray = argv;
}
int foo()
{
std::cout << argumentArray[0]; // or whatever
}

Answer 4

If you're working with MSVC++, then you can use below win32 API to get command line arguments anytime in your program:
GetCommandLine
However, this makes your code non-standard. So it is better if you use main(int argc, char *argv[]) to get the command line arguments and save them for later use, e.g to be used by other functions.