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---
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layout: post
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title: "Pretty-print view in v0.7.3"
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date: 2015-04-11 00:00:00
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excerpt: Automatically reformat structured data with "SHIFT+P".
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---
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I wanted to call out the pretty-print feature in the latest release of lnav.
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This idea came from a coworker of Suresh who was having a hard time trying to
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read some unformatted XML in a log. They wanted the XML pretty-printed and were
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hoping that could be done by just piping the message to xmlpp or the like. So,
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first we implemented the 'pipe-to' and 'pipe-line-to' commands that will let you
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pipe log messages to a command and then display the result inside of lnav. That
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worked well enough, but pretty-printing is such a frequent operation that having
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to execute a command was kind of a pain. It would also be nice if it worked for
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a variety of text, like JSON or Python data. The solution we came up with was to
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leverage the existing code for parsing log messages to create a simple
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pretty-printer that should work for most data formats. Another benefit is that
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the log message does not have to be well-formed for the printer to work, any
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leading or trailing garbage shouldn't confuse things.
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As an example, here is a screenshot of the log message with the unformatted XML
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text with word-wrapping turned on:
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That's not very easy to read and it's hard to figure out the structure of the
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message. Now, here is that same message after pressing SHIFT+P to switch to the
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pretty-print view of lnav:
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The XML text is indented nicely and the usual syntax highlighting is applied.
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Also notice that lnav will automatically try to lookup the DNS name for IP
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addresses. Overall, I think it's a major improvement over the raw view.
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This is a pretty simple feature but I have found it quite useful in the couple
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weeks that it has been implemented. It's so useful that I'm kicking myself for
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not having thought of it before.
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