I have a vector named tokens that holds the command in tokens[0] and args as the rest of the vector. I am trying to convert the vector so I can make the call to execvp(args[0], args); Currently args[0] and args just print as memory addresses.
char **args = (char**)malloc(tokens.size() * sizeof(string));
char *arg;
int i;
for(i = 0; i < tokens.size(); i++)
{
arg = &tokens[i][0];
args[i] = arg;
}
You don't have to resort to malloc to perform this since you are already using vectors of strings.
You could just create a std::vector<char*> before calling execvp:
std::vector<char*> pvec(tokens.size());
std::transform(tokens.begin(), tokens.end(), pvec.begin(), [](auto& str) {
return &str[0];
});
pvec.data(); // This is a char**, pass it to `execvp`
I found that the answer lies with adding the NULL terminator to the end of the vector so that execvp knows where to end pvec.data(); This is thanks to Fatih above.
std::vector<char*> pvec(tokens.size());
std::transform(tokens.begin(), tokens.end(), pvec.begin(), [](auto& str) {
return &str[0];
});
pvec.push_back(NULL);
pvec.data();
pid = fork();
// if we enter child process
if (pid == 0)
{
if (execvp(pvec.data()[0], pvec.data()) == -1)
{
printf("right here officer\n");
}
exit(EXIT_FAILURE);
}```