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

[ryan woodsmall <EMAIL:PROTECTED>]

Not a one-liner, but how about this perlishness:

    #!/usr/bin/perl

    $pos = $ARGV[0];
    $pat = $ARGV[1];

    push(@lines, $line) while($line = <STDIN>);
    for($i = 0; $i < $#lines; $i++){
        print("$lines[$i + $pos]") if($lines[$i] =~ m/$pat/);
    }

Call it with an "after" position and a pattern:

    perl whateveryounameit.pl 9 "[regex]" < inputfile

Should get you what you want.  You could hardcode the position/ 
pattern in for a one-liner.  This will eat a *ton* of memory if you  
have a big input file, as it reads everything into an array.  So be  
careful, no warranty, yada yada yada.

You could do it with regular fread()/sysread()/etc., and seek() ahead  
then rewind back, but that's a bit trickier.

I'm in the process of (slowly) learning Python - anyone have an  
elegant pythonic solution to this problem?

  ryan woodsmall
    EMAIL:PROTECTED


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




On May 3, 2007, at 4:52 PM, Mike Miller wrote:

> On Thu, 3 May 2007, ryan woodsmall wrote:
>
> > 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...
>
> Yes!  That's a good way to do it.  I was actually thinking to  
> myself "how can I add one at the end?" but blocked on the subshell  
> idea (use of parentheses), even though I came up with a (much  
> lamer) subshell-based idea later.  So that solves one problem.  I  
> will use your idea.
>
> But suppose you want to grab the third line after every line with  
> an 'X' in it.  Then we'd want to grab lines with 'match' here  
> because they are three after an X:
>
> X
> X
> skip
> match
> match
> skip
>
> But look what happens:
>
> # cat > foo
> X
> X
> skip
> match
> match
> skip
> ^D
>
> # egrep -A3 X foo
> X
> X
> skip
> match
> match
>
>
> See?  When the second X falls within the three lines following the  
> first X, it just extends the selected region to a fourth line.
>
> This isn't a problem I have to solve because my regions are non- 
> overlapping, but this is potentially a problem for things someone  
> might do some day!  ;-)
>
> Mike
>
> _______________________________________________
> members mailing list
> EMAIL:PROTECTED
> http://mlug.missouri.edu/mailman/listinfo/members


_______________________________________________
members mailing list
EMAIL:PROTECTED
http://mlug.missouri.edu/mailman/listinfo/members