A new question from the front line

bronto has asked for the wisdom of the Perl Monks concerning the following question:

Hello fellow monks

Do you remember the question Save all but line 32!? Yesterday I had another question to which I gave a reply but I am interested again in how you had resolved the same issue. Here we go:

A colleague of mine asked me: "I have a text file that contains data record as lines; here and there between the data you have rows that tell you the names of the columns. If I find a line that contains, say, the word energy I want to print the line that follows it. In similar cases I resolved with awk, but I can't get a solution for this one and I don't want to code it in FORTRAN".

My solution was:

perl -ne 'print scalar <> if /energy/' filename
[download]

He then asked me if I could add a counter, and I slightly modified the previous in:

perl -ne 'print ++$i,scalar <> if /energy/' filename
[download]

What's your solution for this?

Ciao!
--bronto

# Another Perl edition of a song:
# The End, by The Beatles
END {
  $you->take($love) eq $you->make($love) ;
}

Comment on A new question from the front line Select or Download Code

Replies are listed 'Best First'.
Re: A new question from the front line by jmcnamara (Monsignor) on Oct 18, 2002 at 08:31 UTC
Here's another way: `perl -ne 'print if $prev; $prev = /energy/' file # Or with a counter perl -ne 'print ++$i, $_ if $prev; $prev = /energy/' file` [download] Your second solution could have been written as follows: `perl -ne 'print ++$i . <> if /energy/' filename` -- John.	[reply] [d/l] [select]
Re: A new question from the front line by blakem (Monsignor) on Oct 18, 2002 at 08:15 UTC
If you know 'energy' wont occur on successive lines, how about: `perl -pe'$_=/\benergy\b/&&<>'` [download] -Blake	[reply] [d/l]
Re^2: A new question from the front line by Aristotle (Chancellor) on Oct 18, 2002 at 13:57 UTC
His own code doesn't fulfill the successive lines criterion either. Golf time: `perl -pe'$_=/energy/?<>:""'` Hmm, yours beats me if you take out the `\b` though. Makeshifts last the longest.	[reply] [d/l]
Re: A new question from the front line by Chmrr (Vicar) on Oct 18, 2002 at 11:44 UTC
I'd probably do it more or less the same way you did; but for perversity's sake, here's another possibility: `perl -ple 'BEGIN{$/="energy";<>;$.--}/.+/;$_=$..$&' filename` perl -pe '"I lo`+$^X$\"$]!$/"=~m%(.)%s;$_=$1;y^`+*^e v^#$&V"+@( NO CARRIER'	[reply] [d/l]