There is an [eco.json][1] file available which I believe (based on the name) is based on the _Encyclopedia of Chess Openings_.

To give you an idea of the format of the file, here's the entry for _Ruy Lopez: Marshall, Main Line, Spassky Variation_, which happens to be the longest opening in the file:

    {'c': 'C89',
     'f': '5rk1/5ppp/p1pbr3/1p1n3q/P2P2b1/1BPQB1P1/1P1N1P1P/R3R1K1 w -',
     'id': 3320,
     'm': 'e2e4 e7e5 g1f3 b8c6 f1b5 a7a6 b5a4 g8f6 e1g1 f8e7 f1e1 b7b5 a4b3 e8g8 c2c3 d7d5 e4d5 f6d5 f3e5 c6e5 e1e5 c7c6 d2d4 e7d6 e5e1 d8h4 g2g3 h4h3 c1e3 c8g4 d1d3 a8e8 b1d2 e8e6 a2a4 h3h5',
     'n': 'Ruy Lopez: Marshall, Main Line, Spassky Variation'}

  [1]: https://github.com/niklasf/eco