Shell Programming and Scripting

#!/bin/ksh or bash or ...
cat file1 | while read line
do
        grep "^$line$" file2 >/dev/null 2>&1 || echo "$line"
done > output1

oifs="$IFS"
cat file2 | while read line
do
        grep "^$line$" file1 >/dev/null 2>&1 || echo "$line" && continue
        # some other rule, if line exist
        IFS=","
        flds=($line)
        IFS="$oifs"
        first=${flds[0]}
        # some rule here
done > output2

grep -v -f file2 file1 > output1

awk -F, '
t<3{++c[t,$1]}
t==1&&(!($0 in f)) {print > "out1" }
t==2{f[$0]}
t==3&&c[1,$1]!=c[2,$1] { print > "out2"}
' t=2 file2 t=1 file1 t=3 file2