how to sort based on a column but uniq based on another column?

He all, I have a file having some columns开发者_StackOverflow中文版. I would like to do sort for column 2 then apply uniq for column 1. I found this post talking about sort and uniq for the same column but my problem is a little bit different. I am thinking of using something using sort and uniq but don't know how. Thanks.

You can use pipe, however it's not in place.

Example :

$ cat initial.txt
1,3,4
2,3,1
1,2,3
2,3,4
1,4,1
3,1,3
4,2,4

$ cat initial.txt | sort -u -t, -k1,1 | sort -t, -k2,2
3,1,3
4,2,4
1,3,4
2,3,1

Result is sorted by key 2, unique by key 1. note that result is displayed on the console, if you want it in a file, just use a redirect (> newFiletxt)

Other solution for this kind of more complex operation is to rely on another tool (depending on your preferences (and age), awk, perl or python)

EDIT: If i understood correctly the new requirement, it's sorted by colum 2, column 1 is unique for a given column 2:

$ cat initial.txt | sort -u -t, -k1,2 | sort -t, -k2,2
3,1,3
1,2,3
4,2,4
1,3,4
2,3,1
1,4,1

Is it what you expect ? Otherwise, I did not understand :-)

uniq needs the data to be in sorted order to work, so if you sort on second field and then apply uniq on first field, you won't get correct result.

You may want to try

sort  -u -t,  -k1,1 filename | sort -t, -k2,2

Just to be sure that I got what you mean correctly. You want to sort a file based on the second column in the file. Then you want to remove duplicates from the first column (another way of saying applying uniq to column one!). cool, to do this, you need to perform three tasks:

1. sort the column on which uniq is going to be applied (since uniq can work only on sorted input).
2. apply uniq on the sorted column.
3. sort the output based on the values in column two.

Using pipes: The command is

 sort -t ',' -k1  fileName| awk '!x[$1]++' | sort -t ',' -k2

Note that you cannot specify the first field in uniq, you can use the -f switch to jump the first n fields. Hence, I used awk to replace uniq.

I used this sort -t ',' -nk2

here sorts

1,2
2,5
3,1

to

3,1
1,2
2,5