for loop inside of body of email lua script - email

Question

Basically, I have several devices I need to pull data from. I get multiple emails when the temperature measures are under or over the set limits. I would like to have a for loop to include all current devices states that are under or over limits into one email.
body = for device_name, 1 do
device_name++ -- I get error here because unexpected symbol near 'for'
"Device Name: " ..device_name.. "\nDevice Location: " ..device_location..
"\n--------------------------------------------------------------" ..
"\nCurrent Temperature: " ..temperature.." F".. "\nTemperature Limit: ("..
t_under_limit.. "-" ..t_over_limit.. " F)" .."\n\nCurrent Humidity Level: " ..
humidity .. "%".. "\nHumidity Limit: (" .. h_under_limit.. "-" ..h_over_limit.. "%)"
.. "\n\n-------Time Recorded at: " ..os.date().. "-------"})
end, -- end for

Answer 1

there is no variable++ syntax in lua. you need to do
variable = variable + 1
also, you can't assign some for loop construct to a variable. so this statement
body = for device_name, 1, ...
isn't valid. maybe you meant...
local body = ""
for device_name = 1, 1
device_name = device_name + 1
body = body.. "my custom message stuff here"
end

Answer 2

As previously noted, there is no ++ operator in Lua. Also, the syntax for the for loop is different from what you wrote.
I would like to add that the big concatenation afterwards would be much more readable using string.format. Here is an enhanced version of your code, in the form a a function taking a table devices parameters in input, each element being a subtable:
local report_model = [[
Device Name: %s
Device Location: %s
--------------------------------------------------------------
Current Temperature: %d °F
Temperature Limit: (%d-%d °F)
Current Humidity Level: %d %%
Humidity Limit: (%d-%d %%)
-------Time Recorded at: %s-------]]
function temp_report(devices)
local report = {}
for i=1,#devices do
local d = devices[i]
report[i] = report_model:format(d.name, d.location,
d.temperature, d.t_under_limit, d.t_over_limit,
d.humidity, d.h_under_limit, d.h_over_limit,
os.date())
end
return table.concat(report)
end