IFEFFIT: interactive XAFS analysis and FEFF fitting.

IFEFFIT, an interactive program and scriptable library of XAFS algorithms is presented. The core algorithms of AUTOBK and FEFFIT have been combined with general data manipulation and interactive graphics into a single package. IFEFFIT comes with a command-line program that can be run either interactively or in batch-mode. It also provides a library of functions that can be used easily from C or Fortran, as well as high level scripting languages such as Tcl, Perl and Python. Using this library, a Graphical User Interface for rapid 'online' data analysis is demonstrated. IFEFFIT is freely available with an Open Source license. Outside use, development, and contributions are encouraged.