oh my....

thanks a lot !

I thought the solution was something like store keys from file1, iterate them on file2, then reverse the iteration to find missing records... I was far far away from the beauty of awk...

if I understand correctly, awk reads the two files and automagically merged records itself ? It means that there is no need to store values from file1 to compare them to file2 ? Beautifull...

Two things I don't get: the use of the underscore (while i guess it stands for "all read records" ?), and why is END not at the end ?

About the sort command wouldn't it fail on the ';' ? Do you know how to specify 'last field' of line with sort ? Or is something like :
| awk '{ printf substr($NF, 1, length($NF)-1);$NF = "";printf " %s\n",$0 }' | sort -n | awk '{ printf "%s%s;\n",$0,$1 }' | awk '{$1="";sub(/^ +/, "");printf "%s\n",$0}'
preferable ?

Thanks a lot again radoulov ^^