selector is a command line utility for dynamic string selection. As you type a list of substrings separated by ";" or a regexp, the display is updated in real time to show only the matching lines. The main usage of selector is as an efficient search in the shell command history. With the correct option, it will inject the selected line into the terminal input buffer, allowing the user to edit the line and execute it as a standard command.
rlimit is a program that lets you run processes with system resource limits set. It can be used by software developers and testers to test that software will run correctly in resource restricted environments. It is also useful for software which would otherwise consume excessive resources such as programs that used 100% CPU, set their own priority levels, or consume too much memory. This is basically a command line interface to the system functions getrlimit() and setrlimit().