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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.
We have a few lua utility functions available in our utilities submodule. For usage and how to add to them see this page.
We are using the style guide from LuaRocks as documented in https://github.com/luarocks/lua-style-guide#conditional-expressions
For installation, usage and troubleshooting see the luacheck page
We believe this may be due to being in interactive mode. Lua's namespace is declared in chunks, in regular lua a chunk can be the whole file (except in the cases of functions and control structures such as do end, if and for). However, in interactive mode a chunk is one line.
So the variable may have fallen out of scope because the chunk has ended.
You may be able to alleviate this issue by declaring your variable without a value before it is used and then initialising it on a separate line.
For example your variable currently may be: local pvprefix = getMacroValue{macro="MYPVPREFIX}
Change this to:
local pvprefix
pvprefix = getMacroValue{macro="MYPVPREFIX}