Portability of shell scripts from other *nixes

[Doug Poland]

Hello,

I'm trying port some shell scripts to FreeBSD that were originally
written on Darwin (OS X).

The issue I'm having is the shebang line of the scripts in OS X is
#!/bin/sh, and it turns out that is really an instance of bash, and
the code contains some bashisms.  On FreeBSD I have bash in
/usr/local/bin/bash.

Is there an "easy/best" way to have a single shebang that works on
both OS's?  I'd rather not change FreeBSD's bourne shell to bash with
any symlinking of /usr/local/bin/bash to /bin/sh.


-- 
Regards,
Doug