From: Konrad Meyer <konrad@...>
Date: 2007-08-10T18:20:04+09:00
Subject: Re: newbie question: how to seek in a file

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On Friday 10 August 2007 02:09:56 am Konrad Meyer wrote:
> On Friday 10 August 2007 01:43:13 am Ak 756 wrote:
> > I want to find a string in a text file, then read some bytes data after
> > the position of this string. Would anybody kindly help to tell me how to
> > do?
>=20
> If this is what you really want, you can do something like:
>=20
>   READ_BYTES =3D 16
>   my_file_contents =3D File.open('foo'){|f| f.read }
>   my_file_contents =3D~ /find this string(.{#{READ_BYTES}})/
>   my_data =3D $1

Better yet:
  READ_BYTES =3D 16
  content =3D File.open('foo'){|f| f.read }
  my_data =3D content[content.index("find this string"), READ_BYTES]
  # I tried to combine Lutz's and my earlier ideas

Though this of course assumes the string is found.

> Of course, this is no good for large files. Generally if you're trying to
> extract data from a large text file though, you should already know where=
 it
> is (constant width records) or you have to parse through everything before
> the record you want to get at the one you do (csv, xml?).
>=20
> If this is for a configuration file or some sort of semi-static storage, =
I'd
> recommend using YAML or Marshal instead of making your own parser.

=2D-=20
Konrad Meyer <konrad@tylerc.org> http://konrad.sobertillnoon.com/

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