7.2进程切换用户

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

static bool switch_to_user(uid_t user_id, gid_t gp_id)
{
    if ((user_id == 0) && (gp_id == 0))
    {
        return false;
    }

    gid_t gid = getgid();
    uid_t uid = getuid();
    if (((gid != 0) || (uid != 0)) && ((gid != gp_id) || (uid != user_id)))
    {
        return false;
    }

    if (uid != 0)
    {
        return true;
    }

    if ((setgid(gp_id) < 0) || (setuid(user_id) < 0))
    {
        return false;
    }

    return true;
}

int main()
{
    printf("uid:%d  gid:%d\n", getuid(), getgid());

    switch_to_user(1000, 1000);
    printf("uid:%d  gid:%d\n", getuid(), getgid());

    return 0;
}