## how to add column with constant number to each file

Hello
I'd like it if you could help me,
I have a step that reads over 100 text files,
each file contains about 15 lines
I'd like to put a column with a constant number to identify each file,
all this I put in a table

example

file 1
column 1 column 2
xxxxxx ---- 1
xxxxxx ---- 1
xxxxxx ---- 1
xxxxxx ---- 1

file 2
xxxxxx ---- 2
xxxxxx ---- 2
xxxxxx ---- 2

file3
xxxxxx ---- 3
xxxxxx ---- 3
xxxxxx ---- 3

with row number by file does not work because the number is sequential, not independent for each file

I'm sorry about my English.
Thank you very much.

text file imput ------> select values ----------> table output