bibmerge [OPTIONS] BIB_FILE1 BIB_FILE2
bibmerge will merge combine two BibTeX files via one of the following operations -diff, -exclusive, -intersect or -join.
-diff take the difference (asymmetric) between two bib files
-exclusive generate a symmetric difference between two bib files
-h display help information
-intersect generate a bib listing from the intersection of two bib files
-join join two bib files
-l display license
-v display version information
bibmerge -join my-old-articles.bib my-recent-articles.bib
Combine to BibTeX files into one using join.