linux awk comparing two csv files and creating a new file with a flag

Question

I have 2 CSV files that i need to compare and get the difference to a newly formatted file. The samples are given below.

OLD file

DTL,11111111,1111111111111111,11111111111,Y,N,xx,xx
DTL,22222222,2222222222222222,22222222222,Y,Y,cc,cc
DTL,33333333,3333333333333333,33333333333,Y,Y,dd,dd
DTL,44444444,4444444444444444,44444444444,Y,Y,ss,ss
DTL,55555555,5555555555555555,55555555555,Y,Y,qq,qq

NEW file

DTL,11111111,1111111111111111,11111111111,Y,Y,xx,xx
DTL,22222222,2222222222222222,22222222222,Y,N,cc,cc
DTL,44444444,4444444444444444,44444444444,Y,Y,ss,ss
DTL,55555555,5555555555555555,55555555555,Y,Y,qq,qq
DTL,77777777,7777777777777777,77777777777,N,N,ee,ee

Output file

I want to compare the old and new CSV files and to find the changes that has effected in the new file and UPDATE a FLAG to denote these changes

U - if the new file record is UPDATED D - if a record existing in the old file is deleted in the new file N - if a record existing in the new file is not available in the old file

the sample output file is this.

DTL,11111111,1111111111111111,11111111111,Y,Y,xx,xx U
DTL,22222222,2222222222222222,22222222222,Y,N,cc,cc U
DTL,33333333,3333333333333333,33333333333,Y,Y,dd,dd D
DTL,77777777,7777777777777777,77777777777,N,N,ee,ee N

I used diff command but it will repeat the UPDATED record too which is not I want.

 DTL,11111111,1111111111111111,11111111111,Y,N,xx,xx
 DTL,22222222,2222222222222222,22222222222,Y,Y,cc,cc
 DTL,33333333,3333333333333333,33333333333,Y,Y,dd,dd
  ---
 DTL,11111111,1111111111111111,11111111111,Y,Y,xx,xx
 DTL,22222222,2222222222222222,22222222222,Y,N,cc,cc
 5a5
 DTL,77777777,7777777777777777,77777777777,N,N,ee,ee

I used an AWK single line command to filter out my records as well

 awk 'NR==FNR{A[$1];next}!($1 in A)' FS=: old.csv new.csv

the problem with this is is doesnt get me the records only belonging to the OLD file. which is

DTL,33333333,3333333333333333,33333333333,Y,Y,dd,dd

I initiated an driven bash script as well to ahieve this but didnt find much help with a good example.

 myscript.awk

BEGIN { 
        FS = ","    # input field seperator 
        OFS = ","   # output field seperator
}

NR > 1 {
    #flag 
    # N - new record  D- Deleted U - Updated

id = $1
    name = $2
    flag = 'N'

   # This prints the columns in the new order. The commas tell Awk to use the     character set in OFS
    print id,name,flag
}

 >> awk -f  myscript.awk  old.csv new.csv > formatted.csv

Answer 1

This might work for you:

diff  -W999 --side-by-side OLD NEW |
sed '/^[^\t]*\t\s*|\t\(.*\)/{s//\1 U/;b};/^\([^\t]*\)\t*\s*<$/{s//\1 D/;b};/^.*>\t\(.*\)/{s//\1 N/;b};d'
DTL,11111111,1111111111111111,11111111111,Y,Y,xx,xx U
DTL,22222222,2222222222222222,22222222222,Y,N,cc,cc U
DTL,33333333,3333333333333333,33333333333,Y,Y,dd,dd D
DTL,77777777,7777777777777777,77777777777,N,N,ee,ee N

an awk solution along the same lines:

diff -W999 --side-by-side OLD NEW |
awk '/[|][\t]/{split($0,a,"[|][\t]");print a[2]" U"};/[\t] *<$/{split($0,a,"[\t]* *<$");print a[1]" D"};/>[\t]/{split($0,a,">[\t]");print a[2]" N"}'
DTL,11111111,1111111111111111,11111111111,Y,Y,xx,xx U
DTL,22222222,2222222222222222,22222222222,Y,N,cc,cc U
DTL,33333333,3333333333333333,33333333333,Y,Y,dd,dd D
DTL,77777777,7777777777777777,77777777777,N,N,ee,ee N

Answer 2

A good starting point would probably be:

 diff -e OLD NEW

This outputs:

 5a
 DTL,77777777,7777777777777777,77777777777,N,N,ee,ee
 .
 1,3c
 DTL,11111111,1111111111111111,11111111111,Y,Y,xx,xx
 DTL,22222222,2222222222222222,22222222222,Y,N,cc,cc

Meaning that it Added a record on line 5 (5a) and changed the records on lines 1 and 3 (1,3c).

If you can't use this format as-is (which would be good to use a standard) then you would need to write a script which converts it to the format that you describe.