CODEWITHSUNDEEP
c++carrayspointersprogram-entry-point
user3247608
user3247608

Reputation: 593

how to point to char *argv[] in main?

In c++ I've got a main function with 

  int argc, char * argv[]

I need to access the data in argv[] (i.e the arguments) in another function.

I am going to declare a global variable, a pointer to the char **argv.

How do I do this?

Upvotes: 3

Views: 1497

Answers (2)

Angew is no longer proud of SO
Angew is no longer proud of SO

Reputation: 171117

In C++, usually* the best way to handle argv is this:

int main(int argc, char **argv)
{
  std::vector<std::string> args(argv, argv + argc);
}

Now you have args, a correctly constructed std::vector holding each element of argv as a std::string. No ugly C-style const char* in sight.

Then you can just pass this vector or some of its elements as you need.

* It carries the memory & time overhead of dynamically allocating one copy of each argv string. But for the vast majority of programs, command-line handling is not performance-critical and the increased maintainability and robustness is well worth it.

Upvotes: 12

fede1024
fede1024

Reputation: 3098

Global variables should be avoided and you should prefer passing arguments. Anyway, you can just use: 

char **global_argv = NULL;

int main(int argc, char * argv[]){
    ...
    global_argv = argv;
    ...
}

A better way would be:

void my_fun1(int argc, char **argv);  // Passing all the program arguments
void my_fun2(char *arg);              // Passing just the one you need

int main(int argc, char * argv[]){
    ...
    my_fun1(argc, argv);
    my_fun2(argv[3]);                 // Supposing you need the 3rd parameter (fourth on argv)
    ...
}

Upvotes: 6

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