LII. GNU Readline
The readline() functions implement an interface
to the GNU Readline library. These are functions that provide
editable command lines. An example being the way Bash allows you
to use the arrow keys to insert characters or scroll through
command history. Because of the interactive nature of this
library, it will be of little use for writing Web applications,
but may be useful when writing scripts meant to be run from a
shell.
The home page of the GNU Readline project is
http://cnswww.cns.cwru.edu/~chet/readline/rltop.html. It's maintained
by Chet Ramey, who's also the author of Bash.