  Calculating solvent accessible surface areas (SASA) is a run-of-the-mill
calculation in structural biology. Although there are many programs available
for this calculation, there are no free-standing, open-source tools designed
for easy tool-chain integration. FreeSASA is an open source C library for SASA
calculations that provides both command-line and Python interfaces in addition
to its C API. The library implements both Lee and Richards' and Shrake and
Rupley's approximations, and is highly configurable to allow the user to
control molecular parameters, accuracy and output granularity. It only depends
on standard C libraries and should therefore be easy to compile and install on
any platform. The source code is freely available from
http://freesasa.github.io/. The library is well-documented, stable and
efficient. The command-line interface can easily replace closed source legacy
programs, with comparable or better accuracy and speed, and with some added
functionality.
