From: Kristof Bastiaensen <kristof@...>
Date: 2004-08-19T18:41:03+09:00
Subject: Re: Ruby way to update file lines

On Thu, 19 Aug 2004 01:44:10 +0000, Mark Probert wrote:

> Hi.
> 
> I have a need to update a config file.  It uses '#' as a line comment
> marker.  The config file looks like:
> 
>  # file comment
>  #
>  name1:foo1:bar:other
>  name2:foo2:bar:other
>  name3:foo3:bar:other
>  name4:foo4:bar:other
> 
> The name:foo combination is unique.
> 
> What is the most efficient way to read in the file, update the line, and
> then write it back to the file.  One update would be to place a '#' in col
> 1
> 
>  #name3:foo3:bar:other
> 
> Any thoughts appreciated.
> 
> -mark.

You could use inplace edit.  This can make ruby work like awk.
For example:

ruby -aF: -ni.bak -e 'print "#" if $F[0] == "name3"' configfile

KB