string.find using directory path in Lua - perl

Question

I need to translate this piece of code from Perl to Lua
open(FILE, '/proc/meminfo');
while(<FILE>)
{
if (m/MemTotal/)
{
$mem = $_;
$mem =~ s/.*:(.*)/$1/;
}
elseif (m/MemFree/)
{
$memfree = $_;
$memfree =~ s/.*:(.*)/$1/;
}
}
close(FILE);
So far I've written this
while assert(io.open("/proc/meminfo", "r")) do
Currentline = string.find(/proc/meminfo, "m/MemTotal")
if Currentline = m/MemTotal then
Mem = Currentline
Mem = string.gsub(Mem, ".*", "(.*)", 1)
elseif m/MemFree then
Memfree = Currentline
Memfree = string.gsub(Memfree, ".*", "(.*)", 1)
end
end
io.close("/proc/meminfo")
Now, when I try to compile, I get the following error about the second line of my code
luac: Perl to Lua:122: unexpected symbol near '/'
obviously the syntax of using a directory path in string.find is not like how I've written it. 'But how is it?' is my question.

Answer 1

You don't have to stick to Perl's control flow. Lua has a very nice "gmatch" function which allows you to iterate over all possible matches in a string. Here's a function which parses /proc/meminfo and returns it as a table:
function get_meminfo(fn)
local r={}
local f=assert(io.open(fn,"r"))
-- read the whole file into s
local s=f:read("*a")
-- now enumerate all occurances of "SomeName: SomeValue"
-- and assign the text of SomeName and SomeValue to k and v
for k,v in string.gmatch(s,"(%w+): *(%d+)") do
-- Save into table:
r[k]=v
end
f:close()
return r
end
-- use it
m=get_meminfo("/proc/meminfo")
print(m.MemTotal, m.MemFree)

Answer 2

To iterate a file line by line you can use io.lines.
for line in io.lines("/proc/meminfo") do
if line:find("MemTotal") then --// Syntactic sugar for string.find(line, "MemTotal")
--// If logic here...
elseif --// I don't quite understand this part in your code.
end
end
No need to close the file afterwards.