modify a datastream on the fly

Question

I need to hijack and modify a datastream. The stream consists of fixed-width commands. Each command is a new line, and the documentation says that each command starts and ends

Answer 1

Here's a sed version:

sed 'h;s/[^,]*,\([^ ]*\) ETX/\1/;s/./ /g;x;s/,.*/,/;G;s/\n//;s/$/ ETX/'

I'd be willing to bet that not only is the command fixed width, but that the fields are also fixed width. If that's the case then something like this would probably work:

sed 's/\(.\{22\}\).\{9\}\(.\{4\}\)/\1         \2/'

or

sed -r 's/(.{22}).{9}(.{4})/\1         \2/'

or

sed -r 's/STX (.{18}).{9} ETX/STX \1          ETX/'