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Old 06-13-2012, 04:12 PM   #1
AHJ
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Combine awk and grep?


I have two files:

$ cat inds
2
5
3

$ cat family
1 2 3 4
1 5 3 4
1 3 0 0
1 4 0 0
1 7 0 0
1 6 2 7
1 8 2 7

I want to write a new file with all the records in family that are NOT in inds, but matching only in field 2 of family. I foolishly tried

grep -v -f inds family

But of course it matches anywhere in the line, and it removes the last two lines as well because they have the 2 in field 3.

awk '{if($2!="2" && $2!="3" && $2!="5") print $0}' family

would work if my real inds file was not hundreds and hundreds of lines long... So basically, I am looking for something that can inverse-match every pattern from a long long list of patterns, but only for field 2.

I hope this makes sense. Thank you.
 
Old 06-13-2012, 04:38 PM   #2
rknichols
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Among many ways to accomplish that, here's a quickie that will work in awk:
Code:
awk 'ARGIND == 1 { inds[$1] = 1; next } { if( ! ($2 in inds) )  print $0 }' inds family
It reads the entire inds file into an associative array using the first field as the index and setting an arbitrary value, then for each line in the second file (all subsequent files, actually) it checks to see whether field two exists as an index in the inds array.

Last edited by rknichols; 06-13-2012 at 04:40 PM.
 
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Old 06-13-2012, 04:59 PM   #3
AHJ
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Thank you, this is exactly what I was looking for!

I think I even understand how it does it.
 
Old 06-14-2012, 09:36 AM   #4
grail
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I am assuming rk is presenting a full layman version in case you are new, but here is the same code with the superfluous parts removed:
Code:
awk 'FNR==NR{inds[$1];next}!($2 in inds)' inds family
 
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Old 06-14-2012, 01:01 PM   #5
AHJ
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The assumption was correct, I am new. Thank you for the short version, with some googling I think I understand what is going on.
 
  


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