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Searching backwards using regular expressions

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# 1  
Old 01-21-2010
Searching backwards using regular expressions
I'm having trouble writing a regular expression that matches the text I need it to. Let me give an example to express my trouble. Suppose I have the following text:
Code:
if(condition)
	multiline
	statement
else if(condition)
	multiline
	statement
else if(condition)
	multiline
	statement
else if(condition)
	multiline
	statement
else if(condition)
	multiline
	statement
	find me
else if(condition)
	multiline
	statement

I want to find the line "find me" and match everything up from it to the nearest "else if(condition)". There can be anything at all between them, including newline characters. I tried the following regular expression:
Code:
m/else\sif\(condition\)[\s\S]*?find\sme/

Unfortunately the above regular expression does not do what I want. It finds the first "else if(condition)" and selects everything down to the first "find me" despite the nongreedy asterisk. Is there a way to match the "find me" first and then search up for for the "else if(condition)"?


Note: I know the above example doesn't make any sense code-wise. It's not the text I'm trying to match, but it's much less complicated and expresses what I'm trying to accomplish better.
# 2  
Old 01-21-2010
Should be something like:

Code:
awk '
{s=s RS $0}
/else if/{s=$0}
/find me/{print s;exit}
' file

# 3  
Old 01-22-2010
Hi.

I like utility cgrep for situations like this. It allows one to specify conveniently a regular expression for the previous and succeeding boundaries -- "windows":
Code:
#!/usr/bin/env bash

# @(#) s1	Demonstrate previous boundary match 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)
set -o nounset
echo

FILE=${1-data1}

echo " Data file $FILE:"
cat $FILE

echo
echo " Results:"
cgrep -D -w "else if" "find me" $FILE

exit 0

producong:
Code:
% ./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

 Data file data1:
if(condition)
	multiline
	statement
else if(condition)
	multiline
	statement
else if(condition)
	multiline
	statement
else if(condition)
	multiline
	statement
else if(condition)
	multiline
	statement
	find me
else if(condition)
	multiline
	statement

 Results:
else if(condition)
	multiline
	statement
	find me

You will need to obtain, compile, and make available cgrep. See the URL mentioned in the script for that.

Best wishes ... cheers, drl
# 4  
Old 01-22-2010
Code:
tail -r file | nawk '/find me/{p=1}(p){print}(p)&&/ if[(]/{exit}' | tail -r

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