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Here's a solution that doesn't require fudging with SUBSEP, looping through the fields, having the files being pre-sorted, or have a pre-set number of columns/fields :

 mawk -v \_=testfile_001.txt -F/ ' BEGIN { while(getline<_) { __[$!(NF=NF)] } _=close(_)*(FS="^$") } _^($_ in __)' testfile_002.txt 0 14 0 15 0 20 7200 14 7200 15 

• just realized setting FS="^$" for 2nd file is much faster since we're doing line-wide matching, so splitting fields is a waste of time.

Here's a solution that doesn't require fudging with SUBSEP, looping through the fields, having the files being pre-sorted, or have a pre-set number of columns/fields :

 mawk -v \_=testfile_001.txt -F/ ' BEGIN { while(getline<_) { __[$!(NF=NF)] } _*=close(_)*(FS="^$") } _^($_ in __)' testfile_002.txt 0 14 0 15 0 20 7200 14 7200 15 

• just realized setting FS="^$" for 2nd file is much faster since we're doing line-wide matching, so splitting fields is a waste of time.

Tested and proven working on gawk 5.1.1 (including flags -c/-P), mawk 1.3.4, mawk 1.9.9.6, and macos nawk

-- The 4Chan Teller

Here's a solution that doesn't require fudging with SUBSEP, or having the files being pre-sorted, and automatically handles unlimited columns instead of just first 2 :

 mawk -v \_=testfile_001.txt -F/ ' BEGIN { while(getline<_) { __[$!(NF=NF)] } _=close(_)*(FS="^$") } ($_ in __)<NF' testfile_002.txt 0 14 0 15 0 20 7200 14 7200 15 

• just realized setting FS="^$" for 2nd file is much faster since we're doing line-wide matching, so splitting fields is a waste of time.

Here's a solution that doesn't require fudging with SUBSEP, looping through the fields, having the files being pre-sorted, or have a pre-set number of columns/fields :

 mawk -v \_=testfile_001.txt -F/ ' BEGIN { while(getline<_) { __[$!(NF=NF)] } _=close(_)*(FS="^$") } _^($_ in __)' testfile_002.txt 0 14 0 15 0 20 7200 14 7200 15 

• just realized setting FS="^$" for 2nd file is much faster since we're doing line-wide matching, so splitting fields is a waste of time.

Here's a solution that doesn't require fudging with SUBSEP, or having the files being pre-sorted :

 mawk -v \_=testfile_001.txt -F/ ' BEGIN { while(getline<_) { __[$!(NF=NF)] } _=close(_)*(FS=OFS) } !($_ in __)' testfile_002.txt 0 14 0 15 0 20 7200 14 7200 15 

Here's a solution that doesn't require fudging with SUBSEP, or having the files being pre-sorted, and automatically handles unlimited columns instead of just first 2 :

 mawk -v \_=testfile_001.txt -F/ ' BEGIN { while(getline<_) { __[$!(NF=NF)]  } _=close(_)*(FS="^$") } ($_ in __)<NF' testfile_002.txt 0 14 0 15 0 20 7200 14 7200 15 

• just realized setting FS="^$" for 2nd file is much faster since we're doing line-wide matching, so splitting fields is a waste of time.