LinuxQuestions.org - [SOLVED] Compressing a two columned list

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- - Compressing a two columned list (https://www.linuxquestions.org/questions/linux-newbie-8/compressing-a-two-columned-list-4175470630/)

Compressing a two columned list

I have a list of instances in a server cluster and their matching hostname:

Code:

CLUSTER-A HOST1

CLUSTER-A HOST2

CLUSTER-A HOST3

CLUSTER-A HOST4

CLUSTER-B HOST1

CLUSTER-B HOST2

.

.

I'm sure there is a simpler command (awk or sed) that would get me:

Code:

CLUSTER-A HOST1 HOST2 HOST3 HOST4

CLUSTER-B HOST1 HOST2 HOST3 HOST4

.

.

Currently, I write it to an array and process each string- a real pain, so am curious as to a better method.

From my searches (tough to search for something I can't put a name to), I couldn't find much. But I'm sure this is a common issue.

Try:

Code:

#!/bin/sh



awk '

BEGIN {val="";} 

      {

        if (val == $1) printf(" %s",$2);

        else {

              if (val != "") printf("\n");

              val=$1;

              printf("%s %s",$1,$2);

        }

      }

END    { printf("\n");}'

Just redirect the input data into the script, and redirect the output to the result.

NOTE: This assumes the input is sorted.

Another note: I see your output has a "CLUSTER-B HOST1 HOST2 HOST3 HOST4", but the input has no such data.

I was only putting in an example the . . were to imply further data, so your code works great and does exactly what is needed especially since I do a sort prior. Thanks much for your help!