Sorting unique by column - sort command?

Question

I have this file:

hello 1
hello 2
world 1
world 2
hello 3
hi    3
hi    4

I want to sort this like so,

hello 1
hi  3
world 1

The thing is I need only the first unique item in column 1.

I tried sort -k1 -u file.txt but it isn't working as I expect. How do I go about this?

possible duplicate of [Is there a way to 'uniq' by column?](http://stackoverflow.com/questions/1915636/is-there-a-way-to-uniq-by-column) — Ciro Santilli OurBigBook.com, Aug 14 '15 at 12:36

potong · Accepted Answer · 2013-08-21T12:00:00.670

26

This might work for you:

sort -uk1,1 file

This sorts the file on the first field only and removes duplicate lines based on the first field.

edited Aug 21 '13 at 12:00

answered Aug 21 '13 at 10:21

potong

2

Can you please explain this ? – Mariappan Subramanian Aug 21 '13 at 10:43
6

`-k1` sorts from field 1 through the last field (if you had 5 columns, it's identical to `-k1,5`). `-k1,1` sorts on the first and only the first column. – chepner Aug 21 '13 at 12:18

score 8 · Answer 2 · answered Jan 21 '14 at 01:21

Sort and give unique list based on column 1

sort -u -t : -k 1,1 test.txt

-t : = colon is separator

-k 1,1 = based on column 1

Sort and give unique list based on column 1 & column 3

sort -u -t : -k 1,1 -k 3,3 test.txt

-t : = colon is separator

-k 1,1 3,3 = based on column 1 & column 3

score 3 · Answer 3 · answered Aug 21 '13 at 09:55

3

You can pipe it to awk:

sort -k1 file | awk '!($1 in a){a[$1]; print}'
hello 1
hi    3
world 1

answered Aug 21 '13 at 09:55

anubhava

1

Can you please explain above solution – Mariappan Subramanian Aug 21 '13 at 10:37
1

awk command checks `$1` exists in array `a`. If it doesn't exist it prints whole line and stuffs `$1` in array `a`. – anubhava Aug 21 '13 at 10:41
Why sort -k1 -u file.txt doesnt work? Basically here itself we are sorting and removing duplicates based on first column right? – Mariappan Subramanian Aug 21 '13 at 11:09
3

`-k1,1` means start and end at position 1. – anubhava Aug 21 '13 at 11:10

3 Answers3