how extract exact match from a file without grep -w

Question

I have a file A with one colum with a list of strings like this:

I want to use the strings in file A to grep the lines that contains them in file B, and file B looks like this:

1       0/0     ./.     0/1     0/0
12      0/0     0/0     1/1     ./.
1234    1/1     0/1     ./.     0/0
12345   0/0     0/0     1/1     1/1
123456  1/1     1/1     ./.     ./.

In this case, I´m waiting an output that match EXACTLY the strings that are in file A, that looks like this:

12      0/0     0/0     1/1     ./.
1234    1/1     0/1     ./.     0/0

I've used grep -wf A B and it works perfectly, but the problem is that my real files are very heavies and the proces is very costly. Someone have any different idea to get the same results but using other command line?

Does `grep -wFf A B` run faster? (I suspect it might because it uses fixed-string rather than regex matching) — Wintermute, Apr 15 '15 at 08:47
yes!! it runs faster!! both answers are OK, thank you very much!! — user2820398, Apr 15 '15 at 09:00

score 2 · Accepted Answer · answered Apr 15 '15 at 08:35

You can use this awk as an alternative:

awk 'NR==FNR{a[$1]; next} $1 in a' file1 file2
12      0/0     0/0     1/1     ./.
1234    1/1     0/1     ./.     0/0

Explanation:

NR == FNR {                  # While processing the first file
  a[$1]                      # store the 1st field in array a
  next                       # move to next line
}
$1 in a                      # while processing the second file
                             # if 1st field is in array then print it

how extract exact match from a file without grep -w

1 Answers1