Can I setenv() using a envp?

Question

I'm trying to setenv a new environement variable with setenv().

But I noticided that setenv() function set my new environement variable only if I use the environement "extern char **environ"

But I want to use the argument of the main() : "char **envp".

Here's the code I tried to do for setting in envp, but as you will see if you run that code, it won't be set in envp.

But if I use const char **environ it works.

Any ideas ?

#include <stdlib.h>
#include <stdio.h>

int     main(int ac, char **av, char **envp)
{
  int   i;

  i = 0;
  setenv("NEW_ENV_VAR", "hello_world", 0);
  while (envp[i])
    printf("%s\n", envp[i++]);
  return (0);
}

Answer 1

setenv() is documented to not be allowed to change the optional envp argument to main.

If you need to iterate through all the environment variables, use the extern char **environ variable.

See also this question.