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

[Stephen Montgomery-Smith <EMAIL:PROTECTED>]

ryan woodsmall wrote:
> and perl, but i'm sure someone else could do better:
>
>   perl -e 
> 'while($l=<STDIN>){if($l=~m/[PATTERN]/){for($i=0;$i<9;$i++){$l=<STDIN>;}print("$l");}}' 


perl -lne '$f=-10 if /[PATTERN]/;$f++;print if $f==0' file



> yup.
>
>   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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