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Shell Programming and Scripting

Third line occurrence replacement

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# 1  
Old 07-03-2008
Third line occurrence replacement
You guys are really smart, so I'm hoping someone can help me out with this. I would like to match the third line occurrence of a pattern at the beginning of a line in a file and replace it. I'm ok at using sed but I have no clue about this one. Thanks in advance.
# 2  
Old 07-03-2008
What have you tried so far?
# 3  
Old 07-03-2008
Code:
sed "s/^pat1/pat2/" file

But I know it will do it for every occurrence. I've looked through some of the sed options but I can't figure out how to use them for what I'm trying to do.
Last edited by sirokket16; 07-03-2008 at 12:26 PM..
# 4  
Old 07-03-2008
Please provide data sample.
# 5  
Old 07-03-2008
Maybe I should be more clear with the issue I'm having. I want to find the third occurrence at the beginning of a line. So if I have a file that reads:

blah blah
blah
pat1 blah
pat1
pat1 blah // <- find this one and replace with pat2
pat1
.
.
blah

I want to find the third pat1 and overlook the first two.
# 6  
Old 07-03-2008
something like:

Code:
#  awk '{CNT[$1]+=1; if ( $1=="pat1" && CNT[$1]==3 ){print "pat2"} else {print $0}}' blah
blah blah
blah
pat1 blah
pat1
pat2
pat1

should work
Last edited by Tytalus; 07-04-2008 at 07:45 AM.. Reason: tweaked for accuracy - was replacing more than it should
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