If we're going with that assumption (same number of lines, and the keys are in the same order), then it's a one liner in unix shell:

paste  -d\| file1 file2 | cut -d\| -f1,2,5- > file3

I think I prefer jmcnamara's solution with join, though, as it's more forgiving of bad input.

In reply to Re^2: combining 2 files with a comon field by jhourcle
in thread combining 2 files with a comon field by jjohhn

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