It appears that Leopard ships with popular UNIX tools linked against a new BSD-licensed libedit library instead of more popular readline (which was the case in Tiger). This may cause few surprises if you are a hardcore shell prompt surfer. I was especially irritated by Control-R (reverse history search) not working in irb (ruby interactive shell), which was using the new libedit library. The solution to this particular deficiency is very simple -- just configure libedit by editing a file named .editrc in your home directory. Add this line: bind "^R" em-inc-search-prev You can also set many different options in that file -- for more help, run man editrc.

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