I have two files:
1. A huge 8 GB text file. (big_file.txt)
2. A huge list of words approximately 8 million of them. (words_file.txt). Each word is separated by a newline.
What I intend to do is to read each word "w" from words_file.txt and search for that word in big_file.txt. Then extract two words before and after "w" from big_file.txt.
A naive way is to simply run this command below for each of the word.
Code:
while read name
do
grep -owP "(?:\w+\s){0,2}$name(?:\s\w+){0,2}" big_file.txt
done < words_file.txt
But the above code is too slow as the file is being read from the disk several times.
I then tried to store the entire big_file.txt in the memory by modifying the above code (shown below), but still this code is slow. Using "top" command, I can notice that memory usage increases and decreases as if big_file.txt is being read again and again for each "w". I want the big_file.txt to be read just once.
Code:
dump=$(<big_file.txt)
while read name
do
echo $dump | grep -owP "(?:\w+\s){0,2}$name(?:\s\w+){0,2}"
done < words_file.txt
The big_file.txt looks something like this (posting just a small sample of the file):
Code:
in 2004 obama received national attention during his campaign to represent
illinois in the united states senate with his victory in the march democratic
party primary his keynote address at the democratic national convention in july
and his election to the senate in november he began his presidential campaign
in 2007 and after a close primary campaign against hillary rodham clinton
in 2008 he won sufficient delegates in the democratic party primaries to receive
the presidential nomination he then defeated republican nominee john mccain
in the general election and was inaugurated as president on january 20 2009
nine months after his inauguration obama was named the 2009 nobel peace prize laureate
The words_file.txt looks like this (just a sample):
Code:
obama
primaries
water
laureate
computer
The output that the code gives:
Code:
in 2004 obama received national
his inauguration obama was named
democratic party primaries to receive
peace prize laureate
Any suggestions how I can speed up the search and extraction? I am using BASH on Linux.
Last edited by shoaibjameel123; 11-16-2015 at 06:46 AM..
Reason: Edited based on RudiC's comments.
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