[Qgis-user] Field expression for file name?

[nicolas.cadieux at archeotec.ca]

Hi,
I am building an index of a LiDar project (using .las files). I can use 
lasboundary.exe to create .shp boundary polygon for each individual file 
(using the merge option will only create one big polygon).  I can then 
use "vector/data management tools/merge the shapefile to one" to make 
one file.

The problem is I need a field (the file names) for each polygon. Is 
there an field expression for this?

This field is not created by lasboundary or my "merge the shapefile to 
one".  Perhaps I can use the "Advanced Python field calculator" in batch 
mode in the processing plugin but I don't know how to return the files 
names. Can someone help or give my and idea of how to proceed?

Thanks in advance
Nicolas