I have two files that are several hundred MB in size. These files each contain a sorted key. What I would like to do is read each line from each file one at a time. If a match is found, write it out to a “matched” file otherwise write to one of two “nonmatch” files. The main issue that I need to avoid is reading the files into memory. I think I understand how I want to test the condition, what I don't understand is how the looping will work. 
input files
file0    file1    
1         2    
2         4
3         5
5         8
7         9
9

logical test
1<=>2    -1    next 0, keep 1, print to nomatch0
2<=>2     0    next 0, next 1, print to match
3<=>4    -1    next 0, keep 1, print to nomatch0
5<=>4     1    keep 0, next 1, print to nomatch1
5<=>5     0    next 0, next 1, print to match
7<=>8    -1    next 0, keep 1, print to nomatch0
9<=>8     1    keep 0, next 1, print to nomatch1
9<=>9     0    next 0, next 1, print to match

output files
matched    nomatch0   nomatch1
2          1           4
5          3           8
9          7

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In reply to need help reading through two large files and output matches and non matches by jlctx

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