I am trying to write a sed expression to detect lines similer to this:
s0:12345:respawn:/sbin/agetty -8 -s 115200 ttyS0 linux
and replace the "ttys0" with "something_else"
I do not want to detect commented out lines (beginning with #)
I can replace the whole line, but how to I just replace the substring, leaving the rest of the line intact ?