Thread: envp and extern char **environ

What's the difference between environ and envp? They both seem to do the same thing...

environ

Code:

#include <stdio.h>
#include <unistd.h>

extern char **environ;

int main(int argc, char *argv[])
{
        char **p = environ;

        while (*p != NULL)
        {
                printf("%s (%p)\n", *p, *p);
                *p++;
        }

        return 0;
}

envp

Code:

#include <stdio.h>

int main(int argc, char *argv[], char *envp[])
{
        char **p = envp;

        while (*p != NULL)
        {
                printf("%s (%p)\n", *p, *p);
                *p++;
        }

        return 0;
}

I just read that extern char **environ is defined by POSIX while envp (third arg to main) is just something that a lot of implementations support.