sed replace with fixed length

Shell Programming and Scripting
1 
$ cat template
s.noName

$ sed "s/s.no/1/" template > out
$ sed "s/s.no/100/" template >>out

$ cat out
1Name
100Name

1  Name
100Name
2 
sed "s/s.no/1  /" template
3 
sed "s/s.no/$sno/" template >>out
4

Use printf to create the sed script maybe? Or replace everything with three spaces and then overwrite as many as necessary?

5

Do you get the numbers from a file?

Regards

6 
sed 's/^s\.no//' 65152_noname.d | awk ' BEGIN { ctr=1 } { printf("%-3s %-s\n", ctr, $0); ctr+=1 }'
7

yes, I do get the number from input data file

8

Post examples of the 2 files in the exact format.