Several questions about uid

From: music4 (music4_at_163.net)
Date: 02/25/04 

Date: Wed, 25 Feb 2004 17:57:54 +0800

Greetings,

In my program, I want to do this:

char *username; // suppose this var. has value.

if ((pid = fork() == 0)
{
    get uid from username // Question 1: how to do?

    setuid(uid);

    get the uid's home directory // Question 2: how to do?

    execute the uid's .profile //Question 3: how to do?

    setenv("MY_VAR", "aa"); // Question 4: how to handle memory?

    exec("my_program");
}
else if (pid > 0)
{
    waitpid(pid);
}
else
{
    perror("fork error");
}

So there are totally four questions. Please help. Thanks in advance!

Evan