Editing User identifier (section)

===Real user ID===
The real UID (<code>ruid</code>) and real GID (<code>rgid</code>) identify the real owner of the process and affect the permissions for sending signals. A process without superuser privileges may signal another process only if the sender's <code>ruid</code> or <code>euid</code> matches receiver's <code>ruid</code> or <code>suid</code>. Because a [[child process]] inherits its credentials from its parent, a child and parent may signal each other.