Print all lines except those matching a variable with awk [duplicate] - awk

Question

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How to remove the lines which appear on file B from another file A?
(12 answers)
Closed 1 year ago.
I have the following for getting the lines matching a variable using awk:
for i in `cat file1`; do awk -v id="$i" '$0 ~ id' file2; done
How can I do the opposite?
Getting the lines that DON'T match? I think I should use ! somewhere, but don't know where.
File 1 looks like this:
5NX1D
5NX3D
4NTYB
File 2 looks like this:
2R9PA IVGGYTCEENS
2RA3C RPDFCLEPPYT
6HARE YVDYKDDDDKE
4NTYB EYVDYKDDDDD
Output should look like this:
2R9PA IVGGYTCEENS
2RA3C RPDFCLEPPYT
6HARE YVDYKDDDDKE

Answer 1

This is the standard inner join, except we print if a match was not found.
awk 'NR==FNR { a[$1]; next }
!($1 in a)' file1 file2 >newfile2
This is very standard Awk idiom all the way, but very briefly, the line number within the current file FNR will be equal to the overall input line number NR while we are traversing the first input file, file1. If so, we add its contents to the array a, and skip to the next line. Else, if we fall through, we are no longer in the first file; we print if the first field $1 is not in a.
Your original script would be more idiomatic and a lot more efficient phrased similarly (just without the !), too.