Lua

I've added the EPICS Lua support module to our build system. Lua is a scripting language designed to be embedded, it has a small footprint and is reasonably powerful. It would provide an alternative to jumping through hoops in st.cmd syntax but also provides a few other options. All iocsh commands are imported into lua and so you can do things like:

for index=1,10,1
do
    print(string.format("Loading instance: %d", index))
    iocsh.dbLoadRecords("test.db", string.format("P=xxx:,Q=%d", index))
end

You execute files from st.cmd using:

epicsEnvSet("LUA_PATH", "${UTILITIES}/lua")
epicsEnvSet("LUA_SCRIPT_PATH","${TOP}/iocBoot/${IOC}")
luash("file.lua")

or just typing luash puts you into an interactive lua shell.

The lua script record is like a calcout record but can execute lua script. It might be an alternative to e.g. aSub records for parsing stream device strings when writing C is a bit overkill.

As well as being able to read/write PVs there is also some asyn integration into lua, so you can read/write/set asyn parameters from lua command line or script record, or even talk to a device by creating an asyn IP port and sending strings. See the documentation directory in lua support module and the example scripts directory in iocBoot

To use

add    LUA=$(SUPPORT)/lua/master     to configure/RELEASE
add    luaSupport.dbd                to the IOC Makefile DBD list
add    lua   and   asyn              to the IOC Makefile   _LIBS    list

There are examples of a lua script used in the DETADC, Attocube and OERCONE iocs.

There is a powerpoint about lua here: https://indico.cern.ch/event/766611/contributions/3438291/attachments/1856812/3050126/Lang-Lua_Integrating_Scripting_Language.pdf

See also the documentation on our epics-lua module or the actual epics module for more information on using lua in EPICS.

Lua utility functions

We have a few lua utility functions available in our utilities submodule. For usage and how to add to them see this page.

Style Guide

We are using the style guide from LuaRocks as documented in https://github.com/luarocks/lua-style-guide#conditional-expressions

Installing LuaCheck

Either install via the hererocks python script or luacheck by itself. The hererocks way is longer but will integrate with your environment and favourite text editor nicely as it sets up parts such as luacheck.path and luarocks

Via the hererocks python script:

• Download hererocks:
  • Open powershell and navigate to somewhere you would like hererocks to download to
  • Run wget https://raw.githubusercontent.com/mpeterv/hererocks/latest/hererocks.py -OutFile hererocks.py
• Install and activate lua and luarocks:
  • In an EPICS terminal navigate to where you downloaded hererocks.py and run python hererocks.py lua53 -l5.3 -rlatest which installs lua 5.3 into $current directory$\lua53
  • Add $current directory$\lua53\bin to your PATH where current directory is the directory you installed lua 5.3 in
  • Close and reopen your EPICS terminal to allow your PATH to update
• Install luacheck:
  • In your new EPICS terminal run luarocks install luacheck
• Luacheck is now installed

OR install luacheck by itself:

• Go to the luacheck GitHub page and under Windows binary download click the download link which will download the file luacheck.exe
• Place the luacheck.exe file in a useful place e.g. Program Files and add that location to your PATH.
• Restart any command lines you have open.
• Luacheck is now installed

Using luacheck:

Post-install step:

• Set luacheck config:
  • Create a new file .luacheckrc in %LOCALAPPDATA%\Luacheck as this is where luacheck looks for config files
  • Add the below information to the file to set the config

stds.epics_lib = {
    read_globals = {"iocsh", "asyn", "client", "driver", "epics"}
}
stds.utils = {
    globals = {"getMacroValue", "setAsynOptions", "setHardwareFlowControl", "setSoftwareFlowControl"}
}
std = "min+epics_lib+utils"

Note: If you add any functions to our utilities you must add the name of the function to the globals set in std.utils in the .luacheckrc file. Please also add it to our list here, or to one on the repository if we have added it to the repo by then.

Basic usage: luacheck file.lua

For more detailed instructions on the use of luacheck see the luacheck documentation.

The luacheck GitHub page also has information about how to use luacheck in your favourite editor.