Question

I have file like this which contains 5 columns. But some rows in my file have 4 columns by mistake, for example in this file at the 5th and 6th rows, you can see that the second column is missing. I want to replace the missing 2nd column with a blank space without disturbing other rows in my file with field separator “,”.

11111,5323,6296,29-May-2010,1
22222,5323,6296,24-May-2010,1
33333,5323,6296,24-Jun-2010,1
44444,5323,6296,24-Jun-2010,1
55555,8061,15-Jul-2010,1
66666,6296,29-May-2010,1
77777,5323,6296,29-May-2010,1
88888,6296,29-May-2010,1
99999,6296,27-May-2010,1
10101,5323,6296,29-May-2010,1

Output that I need.

11111,5323,6296,29-May-2010,1
22222,5323,6296,24-May-2010,1
33333,5323,6296,24-Jun-2010,1
44444,5323,6296,24-Jun-2010,1
55555,,8061,15-Jul-2010,1
66666,,6296,29-May-2010,1
77777,5323,6296,29-May-2010,1
88888,,6296,29-May-2010,1
99999,,6296,27-May-2010,1
10101,5323,6296,29-May-2010,1

Answer 1

BEGIN{
    FS=","
}

NF==5 { print; }
NF==4 { printf("%s,,%s,%s,%s\n", $1, $2, $3, $4); }