Add numbers to the beginning of every line in a file

Question

How can I add numbers to the beginning of every line in a file?

E.g.:

This is
the text
from the file.

Becomes:

000000001 This is
000         


        

Answer 1

AWK's printf, NR and $0 make it easy to have precise and flexible control over the formatting:

~ $ awk '{printf("%010d %s\n", NR, $0)}' example.txt
0000000001 This is
0000000002 the text
0000000003 from the file.