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This tutorial demonstrates how to use OpenResty’s restydoc command-line utility to quickly lookup OpenResty documentation for Nginx modules, Nginx configuration directives, Lua API functions, Lua C functions, Lua modules, and many more. The restydoc tool was originally inspired by Perl’s perldoc utility.

which restydoc
rpm -qf `which restydoc`

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The restydoc utility is shipped with OpenResty itself. The package name is openresty-doc on Yum-based systems.

The package name is openresty-restydoc on Debian-based systems, like Ubuntu 20.04.

ssh ubuntu20-pkg

which restydoc
dpkg -S `which restydoc`

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We can lookup the docs for the standard Nginx directive rewrite like this.

restydoc -s rewrite

Note the -s option, which means “section”.

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It is extracted from the official Nginx documentation. Under the hood, it invokes the less utility.

We can use the space key to switch to the next page.

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We use the q key to quit.

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Or the standard Nginx’s listen directive.

restydoc -s listen

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Or our OpenResty’s nginx module directives like init_worker_by_lua.

restydoc -s init_worker_by_lua

Standard Lua functions can be looked up too.

restydoc -s string.find

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It is extracted from the official Lua 5.1 reference manual.

Or the standard Lua’s C API functions.

restydoc -s lua_gc

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Or the LuaJIT’s Lua API extension.

restydoc -s ffi.cdef

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Or OpenResty’s own Lua API extension.

restydoc -s

All the restydoc commands above specify the -s option. This is because the displayed docs are all sections from some larger documents.

We can view large documents like a whole Nginx module’s.

restydoc ngx_http_rewrite_module

Here we do not specify the -s option.

It’s much longer, as expected.

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Or a whole Lua module.

restydoc resty.redis

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This is the resty.redis library shipped with OpenResty.

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Or specifying the Lua library name.

restydoc lua-resty-lrucache

To view all the options of restydoc, use the -h option.

restydoc -h

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That’s all I’d like to cover today. Hopefully you’ve found this tool useful.

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About The Author

Yichun Zhang (Github handle: agentzh), is the original creator of the OpenResty® open-source project and the CEO of OpenResty Inc..

Yichun is one of the earliest advocates and leaders of “open-source technology”. He worked at many internationally renowned tech companies, such as Cloudflare, Yahoo!. He is a pioneer of “edge computing”, “dynamic tracing” and “machine coding”, with over 22 years of programming and 16 years of open source experience. Yichun is well-known in the open-source space as the project leader of OpenResty®, adopted by more than 40 million global website domains.

OpenResty Inc., the enterprise software start-up founded by Yichun in 2017, has customers from some of the biggest companies in the world. Its flagship product, OpenResty XRay, is a non-invasive profiling and troubleshooting tool that significantly enhances and utilizes dynamic tracing technology. And its OpenResty Edge product is a powerful distributed traffic management and private CDN software product.

As an avid open-source contributor, Yichun has contributed more than a million lines of code to numerous open-source projects, including Linux kernel, Nginx, LuaJIT, GDB, SystemTap, LLVM, Perl, etc. He has also authored more than 60 open-source software libraries.