Hope I post this right..
cat <inout file> gives me:
FastEthernet0/0 is up, line protocol is up
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 output errors, 0 collisions, 0 interface resets
Serial1/0:0 is up, line protocol is up
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 output errors, 0 collisions, 0 interface resets
Needed output:
FastEthernet0/0 is up, line protocol is up, 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 output errors, 0 collisions, 0 interface resets
Serial1/0:0 is up, line protocol is up, 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 output errors, 0 collisions, 0 interface resets
Output I get running my and your syntax:
$awk 'ORS=NR%3?",":"\n"' test2
, 0 output errors, 0 collisions, 0 interface resetsred
, 0 output errors, 0 collisions, 0 interface resetsred, 0 abort
Entering the input file with vi seems to show that each original line is ended with an end of line correctly (one line doesn't follow onto the next.