Deleting a block of text

[keysorsoze]

Hi I have the following data:

define host {
            hostname win2k3.example.com
            alias domain server
            ip address 10.0.0.1
}
define host {
            alias domain server
            hostname popie.example.com
            ip address 10.0.0.1
}
define host {
            alias domain server
            ip address 10.0.0.20
            hostname srv123.example.com
}

and need help on how to delete a a block based on a match. For example if I wanted to delete win2k3.example.com how would I get rid of the entire block of

define host {
            hostname win2k3.example.com
            alias domain server
            ip address 10.0.0.1
}

I believe this can be done with awk but not sure how since awk is field based rather than line based?

Any tips would be great.

Thanks

[nmset]

There's probably a cleaner way to do it, I'm eager to learn it.

sed can work with adjacent lines to a searched string, but I don't know how to handle it really.

[keysorsoze]

Thank you nmset, can you let me know what the ${tmpID%%:*} is? I understand you are assigning it to the $ID variable but not sure exactly what this is. In addition, how would you loop this through all UNIQUE_STRING matches in a file? I was thinking a for loop but you are using a while.

Thanks

[nmset]

${tmpID%%:*} is to get the line number of the line containing the search string, i.e, win2k3.example.com. It is a bash buil-in functionality for string manipulation. The line in NSOURCE (numbered source file) looks like this from grep -n :

xy: hostname win2k3.example.com

${tmpID%%:*} returns all characters preceding the first match of the split character, here ':' .

how would you loop this through all UNIQUE_STRING matches in a file

I understand from your sample data that you wish to delete one block containing an identifier that is unique in the dataset. If there are more occurences of the identifier, the script is no longer valid. Yet it could be updated.

[drl]

Hi.

For many "window", "paragraph", "segment" searches, copies, extractions, deletions, etc., I find the utility cgrep to be of value. It allows one to specify a regular expression to match a line of interest, and also to specify RE's for matching the boundary lines preceding and succeeding it. For example, on your data in file "data1":

#!/usr/bin/env bash

# @(#) s1	Demonstrate window extraction with cgrep.
# http://www.bell-labs.com/project/wwexptools/cgrep/

echo
set +o nounset
LC_ALL=C ; LANG=C ; export LC_ALL LANG
echo "Environment: LC_ALL = $LC_ALL, LANG = $LANG"
echo "(Versions displayed with local utility \"version\")"
version >/dev/null 2>&1 && version "=o" $(_eat $0 $1) cgrep
set -o nounset
echo

FILE=${1-data1}

echo " Data file $FILE:"
cat $FILE

echo
echo " Results, extract line in window of interest:"
cgrep -w "^define host" +w "^}" "win2k3.example.com" $FILE

echo
echo " Results, invert the behavior:"
cgrep -V -w "^define host" +w "^}" "win2k3.example.com" $FILE

echo
echo " Results, invert the behavior, remove the separator:"
cgrep -D -V -w "^define host" +w "^}" "win2k3.example.com" $FILE

exit 0

which produces the following, showing how one might takes steps to solve: extract the segment within which the string of interest is found, then invert the action -- copy everything except that segment, and finally clean things up a bit:

% ./s1

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")
OS, ker|rel, machine: Linux, 2.6.26-2-amd64, x86_64
Distribution        : Debian GNU/Linux 5.0 
GNU bash 3.2.39
cgrep - (local: ~/executable/cgrep May 29 2009 )

 Data file data1:
define host {
            hostname win2k3.example.com
            alias domain server
            ip address 10.0.0.1
}
define host {
            alias domain server
            hostname popie.example.com
            ip address 10.0.0.1
}
define host {
            alias domain server
            ip address 10.0.0.20
            hostname srv123.example.com
}


 Results, extract line in window of interest:
define host {
            hostname win2k3.example.com
            alias domain server
            ip address 10.0.0.1
}

 Results, invert the behavior:
========================================
define host {
            alias domain server
            hostname popie.example.com
            ip address 10.0.0.1
}
define host {
            alias domain server
            ip address 10.0.0.20
            hostname srv123.example.com
}


 Results, invert the behavior, remove the separator:
define host {
            alias domain server
            hostname popie.example.com
            ip address 10.0.0.1
}
define host {
            alias domain server
            ip address 10.0.0.20
            hostname srv123.example.com
}

The code is found at the URL mentioned at the top of the script source. I have compiled it in both 32 and 64-bit modes.

If you do not like to download, compile, and install code, then you will likely need to learn something like awk or perl to solve this kind of problem.

Best wishes ... cheers, drl

( edit 1: minor typo )

[nmset]

cgrep

I haven't yet tried it but from what you say, I find it a wonderful tool which can save much time. Thank you, drl.