How to pass a vector to execvp

Question

I want to pass a vector in as the second argument to execvp. Is it possible?

Answer 1

Yes, it can be done pretty cleanly by taking advantage of the internal array that vectors use.

This will work, since the standard guarantees its elements are stored contiguously (see https://stackoverflow.com/a/2923290/383983)

#include <vector>

using namespace std;

int main(void) {
  vector<char *> commandVector;

  // do a push_back for the command, then each of the arguments
  commandVector.push_back("echo");
  commandVector.push_back("testing");
  commandVector.push_back("1");
  commandVector.push_back("2");
  commandVector.push_back("3");  

  // push NULL to the end of the vector (execvp expects NULL as last element)
  commandVector.push_back(NULL);

  // pass the vector's internal array to execvp
  char **command = &commandVector[0];

  int status = execvp(command[0], command);
  return 0;
}