Well, it turns out that Apple has decided to use the Z shell for /bin/sh. Zsh is bourne compatible and so it doesn't break anything, yet it seems rather baroque to use a full featured shell intended for interactive use as the standard system /bin/sh. In an email on 27 June 2001, <a href="mailto:firstname.lastname@example.org ">Tim van Holder</a> <a href="http://mail.gnu.org/pipermail/libtool/2001-June/005137.html">said</a> "<i>OS X' /bin/sh is zsh, while Linux uses bash. There have been reports of zsh having terrible performance with the autoconf test suite.</i>" Running <tt>./configure</tt> does seem kinda slow to me in MacOS X. Why has Apple decided to use zsh instead of a minimal, fast and light plain vanilla Bourne shell for /bin/sh?  Actually, it does break some things. See <a href="http://www.publicsource.apple.com/bugs/X/Shells/2416360.html">Darwin bug #2416360</a>. Basically, <tt>time</tt> is a reserved word in the Z-shell and it goofs up when you try to use /usr/bin/time. Some would say it's hugely bloated.