Re: [MLUG] grepping the 9th line after a matching line

[ryan woodsmall <EMAIL:PROTECTED>]

Hmm:

  ( egrep -A9 [pattern] file ; echo "--" ) | egrep -B1 ^--$ | egrep - 
v ^--$

Works?  The echo command throws a trailing "--" at the end of the  
first egrep output, so your input is all the same...

  ryan woodsmall
    EMAIL:PROTECTED


"Be well, do good work, and keep in touch." - Garrison Keillor




On May 3, 2007, at 4:17 PM, Mike Miller wrote:

> You guys have been absolutely amazing on that list question about  
> copying files.  So now I have another question:
>
> Here's a fun problem -- suppose I want to grab the 9th line  
> following a line that matches a pattern.  I think perl may be good  
> for this -- I'm pretty sure I can do it as a one-liner.  But there  
> are "-A" and "-B" options in the GNU version of egrep that simplify  
> this a little.  The "B" and "A" stand for "before" and "after."  So...
>
> egrep -A9 [pattern] file
>
> ...grabs the matching lines and 9 subsequent lines for each match.   
> The problem is that I don't want the first 8 lines from each match.  
> Fortunately, egrep -A gives me a line between each set of 9 that  
> matches the following regexp pattern:  ^--$  That is, it is a  
> single line consisting of nothing but two hyphens.  So this gives  
> me the 9th line following each match but with that darned pair of  
> hyphens still there...
>
> egrep -A9 [pattern] file | egrep -B1 '^--$'
>
> ...so I grep out the extra hyphen lines:
>
> egrep -A9 [pattern] file | egrep -B1 '^--$' | egrep -v '^--$'
>
> That's fairly straightforward but there is one more annoying  
> problem: The last line is not followed by the ^--$ regular  
> expression, so it is lost.  Well, then I can do this but this is  
> getting rather long:
>
> ( egrep -A9 [pattern] file | egrep -B1 '^--$' | egrep -v '^--$' ;  
> egrep -A9 [pattern] file | tail -1 )
>
> Long, but it works except under conditions where the sets of 9  
> lines overlap!  Then it totally screws up.  Luckily, that condition  
> does not arise in my application, so I'm fine with this.
>
> Question:  Is there a better way?
>
> Mike

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