How to replace a column in bash

Question

i have a command that manipulates a particular column in a file.i want to overwrite the output to the same column in the same file.

awk -F' ' '{print $2}' test | awk -F. '{print substr($1,1,7)"."substr($2,1,6)}' |  xargs printf "%014.6f\n"

input:

a 1.1
b 1234567.123456

output:

a 0000001.100000
b 1234567.123456