Alternative of grep in lua script - lua

Question

I have the following text file output.txt that I created (it has 15 colums including symbol | ):
[66] | alert:n | 3.0 | 10/22/2020-14:45:50.066928 | local_ip | 123.123.123.123 | United States of America | SURICATA STREAM ESTABLISHED SYNACK resend with different ACK
[67] | alert:n | 3.0 | 10/22/2020-14:45:51.096955 | local_ip | 12.12.12.11 | United States of America | SURICATA STREAM ESTABLISHED SYNACK resend with different ACK
[68] | alert:n | 3.0 | 10/22/2020-14:45:53.144942 | 123.123.123.123 | local_ip | United States of America | SURICATA STREAM ESTABLISHED SYNACK resend with different ACK
[69] | alert:n | 3.0 | 10/22/2020-14:45:57.176956 | local_ip | 68.73.203.109 | United States of America | SURICATA STREAM ESTABLISHED SYNACK resend with different ACK
[70] | alert:n | 3.0 | 10/22/2020-14:46:05.240953 | 123.123.123.123 | local_ip | United States of America | SURICATA STREAM ESTABLISHED SYNACK resend with different ACK
[71] | alert:n | 3.0 | 10/22/2020-14:46:21.624979 | local_ip | 68.73.203.109 | United States of America | SURICATA STREAM ESTABLISHED SYNACK resend with different ACK
I'm familiar with the bash script, let say if I want to count total specific ip of 123.123.123.123 that can be found in the 9th column, I can implement like this:
#!/bin/bash
ip = "123.123.123.123"
report = output.txt
src_ip_count=$(grep "${ip}" "${report}" | awk '{ print $9 }' | grep -v "local_ip" | uniq -c | awk '{ print $1 }')
and the output is:
[root#me lua-output]# ./test.sh
2
How do I implement the same code above in lua ? I know there is popen function can be used.. but is there a native way to do this in lua ? Also if I use popen, I also need to pass variable $ip and $report inside that command which I'm not sure if it's possible.

Answer 1

There's a bunch of ways to go about this, really. Assuming you read your data from stdin (though the same works for any file you manually open), you can do something like this:
local c = 0
for line in io.lines() do -- or or file:lines() if you have a different file
if line:find("123.123.123.123") -- Only lines containing the IP we care about
if (true) -- Whatever other conditions you want to apply
c = c + 1
end
end
end
print(c)
Lua doesn't have a concept of what a "column" is, so you have to build that yourself as well. Either use a pattern to count spaces, or split the string into a table and index it.

Answer 2

You mentioned that if it is possible to use variable inside popen in lua. It is possible, and you can use grep command in lua.
So in lua you can do this:
-- lua script using grep example
ip = "123.123.123.123"
report = output.txt
local cmd = "grep -F " .. ip .. " " .. report .. " | awk '{ print $9 }' | grep -v 'local_ip' | uniq -c | awk '{ print $1 }'"
local handle = io.popen(cmd)
local src_ip_count = handle:read("*a")
print(src_ip_count)
handle:close()
output:
2