If column 2 of file2 is diferent than column2 of file1 print column1 from file1 and column2 from both files

Question

I have two unsorted files, each with two columns. For any line in file1 whose column1 value matches that of any line in file2, but whose column 2 values differ, I want to print the column 1 value and each column 2 value.

If data from column1 in file 1 does not exist in file2 it can be discarded. I do not need to preserve the sort order in the output file.

file1: 

2222,b2
4444,d4
1111,a1
3333,c3
5555,e5

file2:

2222,8f
5555,e9
4444,7c
3333,c3


OUTPUT file:
2222,b2,8f
4444,d4,7c
5555,e5,e9

Answer 1

Read the 2nd file, save the content into an array (key = 1st field, value = 2nd field) then read the 1st file and check if 1st field is a common key and if the corresponding 2nd field is different. If the result is positive, print the key and the two values:

awk 'BEGIN{FS=OFS=","}NR==FNR{z[$1]=$2;next}
{if (z[$1] && (z[$1]!=$2)){print $0, z[$1]}}' file2 file1

Answer 2

EDIT: The question as originally written was quite unclear and lacked important details. What follows are the original two answers I wrote as the question developed in clarity. The answers are good for similar simpler cases to the question as currently written.

1. For a case of sorted and matching files, I would recommend first using the command line utility paste to create a temporary third file which would be file with with column two of file two added to each line. Pipe the output of this paste command to awk, and then your awk solution becomes trivial - $2 != $4{printf "%s %s %s", $1, $2, $4}.

   paste -d"," file1 file2 | awk 'BEGIN{FS=",";OFS=","}$2 != $4{printf "%s,%s,%s", $1, $2, $4}'

2. For a case of unsorted matched files, if all the keys of file1 and fil2 are identical, just sort the input to the paste. You can do this kind of thing in the bash shell, using process substitution, with the form <( command ), as in the example below:

   paste -d"," <( sort file1 ) <( sort file2 ) | awk 'BEGIN{FS=",";OFS=","}$2 != $4{printf "%s,%s,%s", $1, $2, $4}'

3. For an unsorted and unmatched set of files (the question as currently written), see user don_crissti's answer.

Answer 3

Can I use join ?

sort -o file1 file1 
sort -o file2 file2 
join -t"," -1 1 -2 1 file1 file2 | awk '$2!=$3'