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Asked: 2026-05-27T05:36:56+00:00

I have an awk command that outputs entries absent from $NEWFILE but found in

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I have an awk command that outputs entries absent from $NEWFILE but found in $OLDFILE:

awk -F "|" 'NR==FNR{a[$4]++}!a[$4]' $NEWFILE $OLDFILE > $OUTFILE

This command works great when all entries for an entity sharing a unique identifier are not found in $NEWFILE. However, it fails when only one entry for the entity, but not all, has been removed from $NEWFILE.

Anyone have a suggestion about how I can tweak this awk command to output all the entries absent from $NEWFILE but found in $OLDFILE, regardless of whether all the entries for an entity are removed?

Sample data: newfile, oldfile

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1 Answer

  1. Editorial Team

    If I understand you correctly, this is what you want

    awk -F "|" 'NR==FNR{a[$1 $2 $3 $4]++}!a[$1 $2 $3 $4]' NEWFILE OLDFILE > OUTFILE

    Since NEWFILE don’t have the urls present in OLDFILE the unique row identifier is the composite of the four first fields. Because NEWFILE doesn’t have those urls a simple diff won’t do.

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