replacing text inplace

[Grant Edwards]

On 2008-04-20, Matt Herzog <msh at blisses.org> wrote:

> I'm learning some python with the seemingly simple task of
> updating a firewall config file with the new IP address when
> my dhcpd server hands one out.  Yeah, I know it's dangerous to
> edit such a file "in place"

I don't see how what you're doing is editing a file "in place".

> but this is just an exercise at this point. I would not mind
> using file handles except they seem to add complexity. 

Do you mean file objects?

> The only apparent problem I have with my script so far is that
> it's adding lots of blank lines to the file when it updates
> the IP addresses.

When you do this:

  for line in inputfile:

Each instance of 'line' has a newline at the end of it.

When you do this:

   print line

The print operation adds another newline.  Try it this way:

   print line,

The comma tells print not to append a newline after it has
printed "line".
   
> So "71.146.250.258" needs to change to "71.146.250.223" or something similar.
>
> Is there a saner, cleaner way to do this that won't add new,
> blank lines?

   sed -i s/71.146.250.258/71.146.250.223/g filename

I suppose one probably should escape the dots in the input
regex...
   
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