Replacing strings

[mongster]

I have to replace longer strings with shorter strings,
ex. replacing abcdefg, defgh with xyz

How can I replace strings while retaining/preserving the number of spaces
after the sting?
Because I need to preserve the formating between columns.

ex. abcdefg 123 -> xyz ---123 (here - denotes spaces to preserve)
not abcdefg 123 -> xyz 123

I have tried using sed 's/'"$old_string"'/'"$new_string"'/g'
but the output is grabbed.

TIA,
Mongster

[thedondj]

Does this work?

sed 's/abcdefg/xyz    /g'

What's the output you're getting?