userv is a Unix system facility to allow one program to invoke another when only limited trust exists between them. It is a tool for system administrators, who often find themselves with a program running as one user which needs to be able to do certain things as another user. For example, the author's machine's news system needs to scan its users' newsrcs to ensure that the right newsgroups are fetched. Before userv that part of the news system had to run as root, and clumsily use `su'.
