Read/write file to LM2 connected USB flash

Source code

-- create usb mount directory
os.execute('mkdir -p /mnt/usb')
 
-- find first matching usb storage device
dev = io.readproc('ls /dev/sd*1 2>/dev/null'):match('/dev/sd%l1')
 
-- found it, mount
if dev then
os.execute('mount ' .. dev .. ' /mnt/usb')
alert('[usb-mount] mounted %s', dev)
-- nothing found, local flash will be used
else
alert('[usb-mount] no device found')
end

Read/Write

You can use standard Lua io library functions as well as LM specific helpers for reading/writing whole files at once:

• Reads whole file at once. Return file contents as a string on success or nil on error.

Source code

io.readfile (file)

Writes given data to a file. Data can be either a value convertible to string or a table of such values. When data is a table then each table item is terminated by a new line character. Return boolean as write result when file can be open for writing or nil when file cannot be accessed.

Source code

io.writefile (file, data)

Examples

Write event status to log file

Source code

value = knxdatatype.decode(event.datahex, dt.bool)
data = string.format('%s value is %s', os.date('%c'), tostring(value))
 
-- write to the end of log file preserving all previous data
file = io.open('/mnt/usb/log.txt', 'a+')
file:write(data .. '\r\n')
file:close()

Produced result:

Mon Jan 3 05:25:13 2011 value is false
Mon Jan 3 05:25:14 2011 value is true
Mon Jan 3 05:25:32 2011 value is false
Mon Jan 3 05:25:33 2011 value is true

 

Read data from file (config in format key=value)

Source code

for line in io.lines('/mnt/usb/config.txt') do
  -- split line by '=' sing
  items = line:split('=')
  -- two items, line seems to be valid
  if #items == 2 then
    key = items[ 1 ]:trim()
    value = items[ 2 ]:trim()
    alert('[config] %s = %s', key, value)
  end
end