[blog/bgpscanner-backwards-compat] Add backwards compatibility bgpscanner legacy wrapper script announcement
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title: "New bgpscanner backwards compatibility script released!"
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mobile_menu_title: "bgpscanner compatibility script is out!"
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date: 2021-08-11
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description: "Meet the bgpscanner legacy wrapper - The Micro BGP Suite now provides mostly complete backwards compatibility with Isolario bgpscanner. You may use it to learn bgpgrep & peerindex or to run your legacy scripts easily."
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series: [ "ubgpsuite - The Micro BGP Suite" ]
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categories: [ "news", "development" ]
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tags: [ "ubgpsuite", "bgpscanner", "bgpgrep", "peerindex", "Networking", "BGP" ]
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news_keywords: [ "ubgpsuite", "bgpscanner", "bgpgrep", "peerindex" ]
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---
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## New bgpscanner backwards compatibility script is now available.
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Lately I had the pleasure to be in contact with many old time `bgpscanner` aficionados.
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A question popped up frequently during our conversations.
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* I used to do `X` with `bgpscanner`, can `bgpgrep` do the same, and how?
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That's when the fact hit me, that `bgpscanner` probably had a larger userbase relying
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on it for day to day work than I originally anticipated.
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Unfortunately `bgpgrep` and `peerindex` are not exactly backwards compatible.
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While probably being very convenient to new users, it could throw off
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the experienced userbase that has been familiar with `bgpscanner` for years.
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Even worse, it could make existing scripts instantly unusable.
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This convinced me that providing a backwards compatibility feature might be a good
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idea to help users familiarize with the new tool while also providing a smoother
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transition curve.
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Coming back to the recurring question, yes, `bgpgrep`, and `peerindex`, do
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anything `bgpscanner` can do.
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To top it off, `bgpgrep` does what `bgpscanner` does not.
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That was actually the most fundamental reason that encouraged me to break
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backwards compatibility.
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`bgpgrep` provides extreme flexibility in filtering specification, letting
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the user combine freely multiple conditions and chain them arbitrarily with `AND`,
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`OR` and `NOT` logic.
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Something `bgpscanner` could do only to a very limited extent.
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This while also being intuitive with its syntax.
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But that doesn't eliminate the fact that `bgpscanner` was already pretty powerful
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by itself, and it did things in a different way. So what?
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Enter the [`bgpscanner` legacy wrapper script](https://git.doublefourteen.io/bgp/ubgpsuite/src/branch/master/tools/bgpscanner).
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The third tool in µbgpsuite arsenal (they grow so fast ♥).
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A somewhat pragmatic, crude, grumpy -- yet fascinating in its own special way,
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POSIX shell wrapper script capable of converting (almost) any invocation of
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`bgpscanner` to an equivalent invocation of `bgpgrep` or `peerindex`.
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Making the `bgpscanner` legacy wrapper a drop-in replacement for the
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classic Isolario `bgpscanner`.
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While this is satisfactory by itself, it didn't feel quite alright.
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In my book `bgpscanner` is still an obsolete tool (hence the "legacy" in "wrapper script").
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Being able to actually *learn* how to do things with new tools would be
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much better than relying on the old ways.
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This is when it hit me again, the wrapper script already does all the hard work
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to figure out how to make an equivalent call to µbgpsuite native tools.
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Why not just print the result, instead of executing it?
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```sh
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$ PRETEND=y bgpscanner -i 192.65.131.1 -p "137 2598$" -u 8.8.8.8/32 data/rib/bview.20181016.0800.gz
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bgpgrep -- data/rib/bview.20181016.0800.gz -peer \( 192.65.131.1 \) -supernet \( 8.8.8.8/32 \) -aspath "137 2598$"
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```
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Isn't it awesome? With just a tiny `PRETEND=y` flag, we can now interactively learn
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how to convert an old invocation to the new format.
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True, it might not be the best, most expressive, most idiomatic way to write the query,
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but it is an excellent starting point.
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Obviously, it wouldn't be a true announcement post, if I didn't also mention
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that the `bgpscanner` legacy wrapper script is documented in its own fantastic
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man [page](https://git.doublefourteen.io/bgp/ubgpsuite/src/branch/master/tools/bgpscanner/bgpscanner.1.in).
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And that you're just one command away from having a beautiful PDF with its contents:
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```sh
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$ sed s/@UTILITY@/peerindex/g tools/peerindex/peerindex.1.in | groffer
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```
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Hoping the `bgpscanner` legacy wrapper tool will be at least as useful to you as
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it was fun for me to write.
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Happy hacking!
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Lorenzo Cogotti
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