I’ve recently changed the default shell /bin/sh on my Leopard install to dash from bash. Why would I do this? Well, by bash’s own admission (see BUGS in its manpage), bash is “too big and too slow”. dash is used for /bin/sh by default on Ubuntu nowadays, and it’s a goal for Debian (supposedly for Lenny, but I can’t see it noted in the release notes and it’s only “confirmed” in the Lenny goals). dash is significantly smaller and faster.
Ubuntu and Debian ran into plenty of bashisms when they tried to change, how about Mac OS X? So far I’ve found problems with /usr/libexec/path_helper (I just changed the shebang line to #!/bin/bash). There was also a problem with X11’s startx, and my patch was quickly committed.
Interestingly enough, when I went to move the sh binary, there are actually two versions of bash in /bin. Both report
GNU bash, version 3.2.17(1)-release (i386-apple-darwin9.0)
but differ at the binary level (they aren’t even the same size). I wonder if Apple tried to optimize their /bin/sh given that it gets more usage.
I built dash-0.5.5.1 from the tarball without a problem.