If you do not have a liberty file but want to test this synthesis script,
you can use the file techlibs/cmos/cmos_cells.lib from the yosys sources.
+Various more complex liberty files (for testing) can be found here:
+
+ http://vlsiarch.ecen.okstate.edu/flows/MOSIS_SCMOS/latest/..
+ ../cadence/lib/tsmc025/signalstorm/osu025_stdcells.lib
+ ../cadence/lib/ami035/signalstorm/osu035_stdcells.lib
+ ../cadence/lib/tsmc018/signalstorm/osu018_stdcells.lib
+ ../cadence/lib/ami05/signalstorm/osu05_stdcells.lib
+
Yosys is under construction. A more detailed documentation will follow.