From: Robert Klemme <bob.news@...>
Date: 2003-06-24T19:25:59+09:00
Subject: Re: Operate on a range of lines in a file.


"Brian Candler" <B.Candler@pobox.com> schrieb im Newsbeitrag
news:20030624075527.GC57124@uk.tiscali.com...
> On Tue, Jun 24, 2003 at 11:02:58AM +0900, Jim Bob wrote:
> > I'm hoping someone can jog my memory here. Say I've got a file which
> > contains the keywords "START" and "END", with several lines in
between.
> > Suppose I want to operate on everything between START and END
(inclusive
> > or not, doesn't really matter, I don't think).
> >
> > Naively, I would do one of a couple things: either use a multiline
> > regexp, or read the file until START is encountered, and set some sort
> > of "readthis" flag which signals the program to operate on the lines
> > until END is encountered, at which point the flag is unset.
> >
> > *However*.... I'm pretty sure that, somewhere, sometime, I saw some
much
> > more elegant way of doing this in ruby. I said "neat!", and promptly
> > forgot about it. Something involving ranges, maybe? Anybody have an
idea
> > what I might have been thinking of, or am I misremembering?
>
> while line = gets
>   if line =~ /^START$/ .. /^END$/
>     puts line
>   end
> end
>
> ('puts line' will ping all lines between and including the START and END
> lines)

There might be a hidden gotcha in your code if it worked for you: $_ will
be assigned during gets and this might have made it work (if at all).
However, it didn't work for me:

irb(main):054:0* lines="1\nSTART\nfoo\nEND\n2"
"1\nSTART\nfoo\nEND\n2"
irb(main):055:0>
irb(main):056:0* lines.each do |line|
irb(main):057:1*   if line =~ /^START$/ .. /^END$/
irb(main):058:2>     puts line
irb(main):059:2>   end
irb(main):060:1> end
START
"1\nSTART\nfoo\nEND\n2"
irb(main):061:0>

IMHO this is the correct solution:

irb(main):062:0* lines.each do |line|
irb(main):063:1*   if /^START$/ =~ line .. /^END$/ =~ line
irb(main):064:2>     puts line
irb(main):065:2>   end
irb(main):066:1> end
START
foo
END
"1\nSTART\nfoo\nEND\n2"
irb(main):067:0>

Regards

    robert