When dealing with hundreds of shots, it could be painful to change the render filepath manually. So I wrote a script to automate this task based on .blend file name.
For example, I organise my files to be named like – S05C04_20120727.blend
Where S = scene, C = cut, and those 8 digits are the date this file has been changed.
I like my render filename to be the same with blend file but strip the date part out.
So, in Text Editor, paste this script
currentfilename = bpy.path.display_name_from_filepath(bpy.data.filepath)
#this will store the current file name (with ".blend" truncated)
#into a variable called "currentfilename"
#so now, currentfilename hold a string 'S05C04_20120727'
renderfilepath = '//../render/'+currentfilename[:-9]+'/'+currentfilename[:-8]
#the [:-9] means truncate last 9 charactors out of the string
#so currentfilename[:9] would be 'S05C04'
#and currentfilename[:-8] would be 'S05C04_'
#renderpath variable would be '//../render/S05C04/S05C04_'
bpy.data.scenes['Scene'].render.filepath = renderfilepath
#don't forget to change 'Scene' to your actual scene name
Now press ‘Run Script’, you’ll see the render filepath change.
You can run this script with other blend file as well. For running from command line without opening the GUI, You have to add another line at the end
#to save changes that you've made.
and save it as a .py, like – renderpath.py
Now, from command line, run
blender -b S03C12_20120727.blend -P renderpath.py
This will change the setting inside the S03C12_20120727.blend file without the need to run Blender GUI.