I have some logic which uses CAT to concatenate group of files, 'SED'-ing some field values and piping the output to one file :-

cat `echo $infilename|sed '{
s/.filestream./'${file_stream}'/g
s/.field2./'${jobopt2}'/g
s/.sb_odate./'${SB_ODATE}'/g
}'` >$outfilename

Now I need to stream the output of that operation to two output files, conditional on the value of the first character of each line of the input files......if the first character is 7 or 8 write the record to one output and if not write it to the alternative output file

I know I could read through the group of input files and add a grep........but can anyone suggest a way of doing it with just one read through the input ?