LinuxQuestions.org - [SOLVED] Matching Between Two Files:

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Matching Between Two Files:

I have two files, a.txt and b.txt. The file a.txt (3 columns) is containing the data in file b.txt (1 column) and more. What I am looking to do is to search in a.txt for each element in b.txt, and print its corresponding line. Here is a partial cut of the two big files:

a.txt

Code:

planetlab4-dsl.cs.cornell.edu        42.4436    -76.4816

planetlab2.cs.purdue.edu        40.4274    -86.9167

planet2.scs.cs.nyu.edu        40.7292    -73.9937

planetlab2.cnis.nyit.edu        40.814    -73.6081

ricepl-1.cs.rice.edu        29.7225    -95.3924

pl1.eecs.utk.edu        35.9483    -83.9367

pl2.eecs.utk.edu        35.9483    -83.9367

planetlab2.itwm.fhg.de        49.26    7.46

planetlab06.cs.washington.edu        47.6531    -122.313

planetlab2.cs.ubc.ca        49.2637    -123.237

pub1-s.ane.cmc.osaka-u.ac.jp        34.81    135.52

pub2-s.ane.cmc.osaka-u.ac.jp        34.81    135.52

planetlab1.citadel.edu        32.7984    -79.9614

planetlab2.citadel.edu        32.7984    -79.9614

pl2.ernet.in        28.6    77.09

planetlab3.inf.ethz.ch        47.3794    8.54513

planetlab4.inf.ethz.ch        47.3794    8.54513

b.txt

Code:

planetlab2.cnis.nyit.edu

planetlab1.cs.purdue.edu

planetlab2.cs.purdue.edu

planet3.cs.ucsb.edu

planetlab1.cs.colorado.edu

planetlab02.sys.virginia.edu

planet1.cs.rochester.edu

planetlab2.byu.edu

planetlab06.cs.washington.edu

planetlab04.cs.washington.edu

out.txt

Code:

planetlab2.cnis.nyit.edu        40.814    -73.6081

planetlab2.cs.purdue.edu        40.4274    -86.9167

planetlab06.cs.washington.edu        47.6531    -122.313

So, the script will look for each line in b.txt in the first column in a.txt, and if a match found, it will print that 3 columns corresponding line from b.txt in out.txt. In this example just 3 matches were found.

Here's one possible solution.

Hash the contents of file a, then look up the fields in file b. If there's a match, print it.

Code:

#!/bin/bash



declare -A servers



function hash_contents() {

    while read line; do

        fields=($line)

        servers[${fields[0]}]="${fields[1]}\t${fields[2]}"

    done < $@

}



function lookup_fields() {

    while read line; do

        [ ! -z "${servers[$line]}" ] && \

            echo -e $line'\t'${servers[$line]}

    done < $@

}



hash_contents a.txt

lookup_fields b.txt



exit 0

Worked perfectly, thanks a lot.

All the best

There is also the command join:

Code:

$ join <(sort a.txt) <(sort b.txt)

planetlab06.cs.washington.edu 47.6531    -122.313

planetlab2.cnis.nyit.edu 40.814    -73.6081

planetlab2.cs.purdue.edu 40.4274    -86.9167

Quote:

Originally Posted by Reuti (Post 4551501)

There is also the command join

Ah! Just totally pwned my solution with a one-liner.

Quote:

"Those who don't understand UNIX are condemned to reinvent it, poorly." – Henry Spencer

Anyhow, good solution.