From: William James <w_a_x_man@...>
Date: 2006-07-31T07:35:12+09:00
Subject: Re: Howto Delete 3 Leftmost Characters


Skeets wrote:
> Esteban Manchado Vel�zquez wrote:
> > On Mon, Jul 31, 2006 at 06:30:13AM +0900, Skeets wrote:
> > > i'm sure this is easy, but i've gone through Pickaxe's string methods,
> > > searched the web and searched the groups, and i can't figure out how to
> > > do this in Ruby.
> > >
> > > i grep a file and it returns the following string:
> > >
> > > #ip 127.0.0.1
> > >
> > > i now want to get rid of "#ip" so i can then strip the remaining string
> > > to get rid of spaces.
> > >
> > > however, i can't find out how to delete the 3 leftmost characters - in
> > > this case "#ip".
> >
> >     "#ip 127.0.0.1"[3..-1] # => " 127.0.0.1"
> >     "#ip 127.0.0.1"[4..-1] # => "127.0.0.1"
> >
> > But you're probably better off using regular expressions instead of fixed
> > indices:
> >
> >     "#ip 127.0.0.1".sub(/^#ip\s+/, '') # => "127.0.0.1"
> >
> > That is, "remove, from the beginning of the line, '#ip' followed by one or
> > more space characters (be them spaces, tabs or whatever)". If you don't know
> > regular expressions, _and_ you're into text processing, I recommend you to go
> > and read some book about regular expressions and practice a little (under
> > Linux there are a couple of handy utilities for that; I'm sure there must be
> > also for other platforms).
> >
> >     Regards,
> >
> > --
> > Esteban Manchado Vel�zquez <zoso@foton.es> - http://www.foton.es
>
> Esteban, and all - thank you.
>
> this did the trick...
>
> if File.exist?( 'current_ip.txt' )
>
>   f = File.open('current_ip.txt').grep(/#ip/)
>   f = f[0].sub(/^#ip\s+/, '')
>
> end
>
> puts f
>
> the File.open grep line returned an array.  i had to sort that out
> first.  i know this file will always have only one instance of #ip - is
> there any way to force grep to return as a variable instead of an
> array?
>
> also, i believe the regex Esteban gave will get rid of all white spaces
> - both to the left and right of the ip address.
>
> thanks to everyone for the help.

file_name = 'current_ip.txt'
if File.exist?( file_name )
  ip = File.read( file_name )[ /^#ip\s+([\d.]+)/, 1 ]
end
p ip