CODEWITHSUNDEEP
bashshellscripting
Kunal Saha
Kunal Saha

Reputation: 19

Want to delete few lines above and below certain string

My requirement is to delete certain lines from my nagios file

Below mentioned is a part of my hotname.cfg file. My requirement is to make a shell script to delete lines beginning from "define host {" upto "}" and the variable input ( read ) to fetch from user is just the host_name which can differ.

here i want to delete all entries relevant to host_name --> hostname02x so i need to delete entries relevant to it beginning from "define host {" upto "}" , so that the file which earlier look 

#cat hostname.cfg

define host{
                use                     linux-server            ; Name of host template to use
                host_name               hostname01x
                hostgroups              COT-Servers
                contact_groups          admins
                alias                   FEA Preprod
             }

define host{
                use                     linux-server            ; Name of host template to use
                host_name               hostname02x
                hostgroups              COT-Servers
                contact_groups          admins
                alias                   Grid Engine
              }

looks like...

#cat hostname.cfg

define host{
                use                     linux-server            ; Name of host template to use
                host_name               hostname01x
                hostgroups              COT-Servers
                contact_groups          gecotadmins
                alias                   FEA Preprod
             }

I used several methods to delete such entry but none of my algorithms works perfectly.

Upvotes: 0

Views: 93

Answers (3)

sjsam
sjsam

Reputation: 21955

If you wish to use a shell script, try this

#!/bin/bash
awk  -v hostname=$2 'BEGIN{RS="}\n"}!($0~hostname) {if($0!="\n"){printf "%s}\n",$0}}' $1 >tempfile.cfg
mv tempfile.cfg $1

Save the script as, say, remove_host

and run it as 

./remove_host hostname.cfg host_to_remove

Upvotes: 0

SLePort
SLePort

Reputation: 15461

With sed :

sed '/define host/ {:a;/}/!{N;ba};/hostname02x/d}' hotname.cfg

It loops over all blocks from /define host/ upto next } : each line in block is added to the pattern space with N and the pattern space matching hostname02x is deleted.

Explanation :

  • /define host/ : starting from /define host/
  • :a : a label for upcoming loop
  • /}/! : if } is not found...
  • N : append the line to the pattern space
  • ba : branch to label a to check if next line contains a }
  • when loop ends, } has been found
  • /hostname02x/d : deletes the pattern space if it matches /hostname02x/

Upvotes: 1

Kent
Kent

Reputation: 195039

this awk one-liner should work for given example:

awk -v RS="[}]\n" -v ORS="}\n" '!/hostname02x/' hostname.cfg

The idea is, make the {...} block as a record, and check if the record has hostname02x, we skip the record.

Upvotes: 4

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