Pattern matching - FAST code

Pattern matching example from a Well House Consultants training course
More on Pattern matching [link]

This example is described in the following article(s):
• Making a Lua program run more than 10 times faster - [link]

Source code: slander1 Module: U108

--[[ This is a pattern matching example that goes through
a data file of 43 Mbytes and finds all log file records which
are Google search engine arrivals.

In this (the faster of two example), I have matched section by
section to make the code run quickly - it turns out to be 1000
times faster than a starightforward single match. ]]

fh = io.open("ac_short")
running = true

mcount = 0
count = 0

while running do
        line = fh:read()
        if line ~= nil then
                count = count + 1
                n,m = string.find(line,'%.google%.')
                if n ~= nil then
                        n,m,ip = string.find(line,'(%S+)')
                        n,m,query = string.find(line,'"http.-[&?]q=(.-)[&"]')
                        if query ~= nil then
                                mcount = mcount + 1
                                print (count,mcount,ip,query)
                        end
                end
        else
                running = false
        end
end
taken = os.clock()
print ("time taken in seconds - ",taken)

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This module and example are covered on the following public courses:
* Learning to program in Lua
* Lua Programming
* Lua Programming
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Other Examples

This example comes from our "Pattern matching" training module. You'll find a description of the topic and some other closely related examples on the "Pattern matching" module index page.

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