Grep rows with a length of 3 - linux

Question

Hi i have a table which looks like this:
chr10 84890986 84891021 2 17.5 2 93 0 61 48 2 48 0 1.16 GA
chr10 84897562 84897613 2 25.5 2 100 0 102 50 49 0 0 1 AC
chr10 84899819 84899844 2 12.5 2 100 0 50 0 0 52 48 1 GT
chr10 84905282 84905318 6 5.8 6 87 6 54 80 19 0 0 0.71 AAAAAC
chr10 84955235 84955267 2 16 2 100 0 64 50 0 0 50 1 AT
chr10 84972254 84972288 2 17 2 93 0 59 2 0 47 50 1.16 GT
chr10 85011399 85011478 3 25.7 3 80 12 63 58 1 40 0 1.06 GAA
chr10 85011461 85011525 3 20.7 3 87 6 74 39 0 60 0 0.97 GAG
chr10 85014721 85014841 5 23.8 5 78 8 66 0 69 0 29 1 TTCCC
chr10 85021530 85021701 5 38.4 5 84 13 53 74 0 24 0 0.85 AAGAG
chr10 85045413 85045440 3 9 3 100 0 54 66 33 0 0 0.92 CAA
chr10 85059334 85059364 5 6 5 92 0 51 20 3 0 76 0.92 ATTTT
chr10 85072010 85072038 2 14 2 100 0 56 50 50 0 0 1 CA
chr10 85072037 85072077 4 10 4 84 10 55 25 22 0 52 1.47 ATCT
chr10 85084308 85084338 6 5 6 91 0 51 83 13 3 0 0.77 CAAAAA
chr10 85096597 85096640 3 14.7 3 95 4 79 69 30 0 0 0.88 AAC
chr10 85151154 85151190 6 6.5 6 87 12 51 0 11 0 88 0.5 TTTCTT
chr10 85168255 85168320 4 16.2 4 100 0 130 50 0 49 0 1 AGGA
chr10 85173155 85173184 2 14.5 2 100 0 58 48 0 0 51 1 TA
chr10 85196836 85196861 2 12.5 2 100 0 50 52 48 0 0 1 AC
chr10 85215511 85215546 2 17.5 2 100 0 70 51 48 0 0 1 AC
chr10 85225048 85225075 2 13.5 2 100 0 54 51 48 0 0 1 AC
chr10 85242322 85242357 2 17.5 2 93 0 61 0 2 48 48 1.16 TG
chr10 85245934 85245981 4 11 4 79 20 51 27 2 0 70 0.99 ATTT
chr10 85249139 85249230 5 18.8 5 88 6 116 0 60 0 39 0.97 TTCCC
chr10 85251100 85251153 5 11 5 97 2 92 0 0 37 62 0.96 GTTTG
chr10 85268725 85268752 4 6.8 4 100 0 54 0 25 0 74 0.83 CTTT
chr10 85268767 85268798 4 7.8 4 100 0 62 0 0 22 77 0.77 TTTG
chr10 85269189 85269239 6 8.8 6 79 16 54 84 2 12 2 0.8 AAAAGA
chr10 85330217 85330253 2 18 2 100 0 72 0 0 50 50 1 TG
chr10 85332256 85332314 4 15 4 82 7 75 70 1 27 0 0.97 AAGA
chr10 85337969 85337996 2 13.5 2 100 0 54 0 0 48 51 1 TG
chr10 85344795 85344957 2 75.5 2 83 12 198 45 4 3 45 1.42 TA
chr10 85349732 85349765 5 6.8 5 93 6 59 84 15 0 0 0.61 AAAAC
chr10 85353082 85353109 5 5.4 5 100 0 54 0 22 18 59 1.38 CTGTT
I want to extract all rows with have 3 and only 3 characters in the last column. My try till now is this:
grep -E "['ACTG']['ACTG']['ACTG']{1,3}$"
But this gives me everything from 3 and longer than 3. I tried many different combinations but nothing seems to give me what i want. Any ideas?

Answer 1

If you like to try awk, you can do:
awk '$NF~/\<...\>/' file
chr10 85011399 85011478 3 25.7 3 80 12 63 58 1 40 0 1.06 GAA
chr10 85011461 85011525 3 20.7 3 87 6 74 39 0 60 0 0.97 GAG
chr10 85045413 85045440 3 9 3 100 0 54 66 33 0 0 0.92 CAA
chr10 85096597 85096640 3 14.7 3 95 4 79 69 30 0 0 0.88 AAC
It will test if last field $NF has 3 character ...
This regex would also do: awk '$NF~/^...$/'
Or if you need exact characters. (PS this needs awk 4.x, or use of switch --re-interval)
awk '$NF~/^[ACTG]{3}$/' file
Using grep
grep -E " [ACTG]{3}$" file
chr10 85011399 85011478 3 25.7 3 80 12 63 58 1 40 0 1.06 GAA
chr10 85011461 85011525 3 20.7 3 87 6 74 39 0 60 0 0.97 GAG
chr10 85045413 85045440 3 9 3 100 0 54 66 33 0 0 0.92 CAA
chr10 85096597 85096640 3 14.7 3 95 4 79 69 30 0 0 0.88 AAC
You need the space, to separate last column, and {3} to get 3 and only 3 characters.

Answer 2

If you want to print the rows which has exactly three chars in the last column then you could use the below grep command.
grep -E " [ACTG]{3}$"
[ACTG]{3} Matches exactly three characters from the given list.

Answer 3

You have to grep either " ['ACTG']['ACTG']['ACTG']$" or " ['ACTG']{1,3}$".
Currently, you are grepping 3 to 5 'ACTG'.
Also, the quotes are unnecessary ['ACTG'] means "match anything between []" so any of the 5 characters 'ACTG, just grep " [ACTG]{1,3}$".
Be sure to use a delimiter for the left part (space ' ', tab\t if it is tab delimited, word boundary \b or \W).
If your lines are all ending with [ACTG]+, you can even only grep -E "\W.{,3}$"

Answer 4

Another way that you could do this would be using awk:
$ awk '$NF ~ /^[ACTG][ACTG][ACTG]$/' file
chr10 85011399 85011478 3 25.7 3 80 12 63 58 1 40 0 1.06 GAA
chr10 85011461 85011525 3 20.7 3 87 6 74 39 0 60 0 0.97 GAG
chr10 85045413 85045440 3 9 3 100 0 54 66 33 0 0 0.92 CAA
chr10 85096597 85096640 3 14.7 3 95 4 79 69 30 0 0 0.88 AAC
This prints all lines whose last field exactly matches 3 of the characters "A", "C", "T" or "G".

Answer 5

2 hours late but this is one way in awk
This can be easily edited for different lengths and fields.
awk 'length($NF)==3' file

Answer 6

As i was looking for answers myself i found out that Perl regex work more efficiently:
this does the deal : grep -P '\t...$' Way more compact code.
$ cat roi_new.bed | grep -P "\t...$"
chr10 81038152 81038182 3 9.7 3 92 7 51 30 0 0 70 0.88 TTA
chr10 81272294 81272320 3 8.7 3 100 0 52 0 30 69 0 0.89 GGC
chr10 81287690 81287720 3 10 3 100 0 60 66 33 0 0 0.92 CAA