mjhjmtu

I have a list like this:

2017-12-11 AAOI 40.33
2017-11-15 AAOI 44.3492
2017-12-15 AEIS 70.98
2017-11-15 AEIS 80.137
2017-10-23 AIEQ 25.1601
2017-11-15 AMBA 52.6501
2017-12-05 ATHM 57.2
2017-11-09 AUDC 7.02
2017-12-22 BEW 0.58
2017-10-17 BIOP 8.19
2017-12-08 BLDP 4.86
2017-12-21 BLOC 2.3
2017-12-12 BLOC 2.7
2017-12-11 BLOC 2.32
2017-12-04 BLOC 2.39
2017-11-27 BLOC 2.6
2017-11-15 BOX 21.63
2017-12-22 BTL 10.5638
etc.

I want to get the first (most rescent) match for each symbol, symbol held in second column. With the sample input above this should be the output:

2017-12-11 AAOI 40.33
2017-12-15 AEIS 70.98
2017-10-23 AIEQ 25.1601
2017-11-15 AMBA 52.6501
2017-12-05 ATHM 57.2
2017-11-09 AUDC 7.02
2017-12-22 BEW 0.58
2017-10-17 BIOP 8.19
2017-12-08 BLDP 4.86
2017-12-21 BLOC 2.3
2017-11-15 BOX 21.63
2017-12-22 BTL 10.5638

The list is already sorted by column 2 ascending, then column 1 descending.

I am thinking along the lines of using awk to set the matching pattern to $2 (second column) and pipe matches based on this pattern into head.

This is not the first unique occurrence; it is the first unique occurrence where uniqueness is based on column 2 only. Like a uniq by column and return first occurrence only. Accordingly generous with the tags.

I fail connecting the dots. How would you do it?

Two ways to do it:

sort sort -u -k2,2 infile
awk awk -F" " '!_[$2]++' infile

I have done this by awk and sed combination.

for w in `cat filename | awk 'print $2' | sort | uniq`; do sed -n '/'$w'/p' filename| sed -n '1p'; done 

output

2017-12-11 AAOI 40.33
2017-12-15 AEIS 70.98
2017-10-23 AIEQ 25.1601
2017-11-15 AMBA 52.6501
2017-12-05 ATHM 57.2
2017-11-09 AUDC 7.02
2017-12-22 BEW 0.58
2017-10-17 BIOP 8.19
2017-12-08 BLDP 4.86
2017-12-21 BLOC 2.3
2017-11-15 BOX 21.63
2017-12-22 BTL 10.5638