From: Thomas Pierce <ruby@...>
Date: 2008-02-18T23:35:26+09:00
Subject: Re: Help with Writing Replacement Text to Files

Andy/Jeremy

Thanks for the help!

Jeremy, I ran your code snippet first with "w+" and it wiped the whole  
file. I then ran the code snippet Andy provided and it worked. I went  
back and used "r+" instead of "w+" in the code you provided Jeremy and  
it worked as well.

I also appreciate the explanatory comments. Very helpful.

Both code snippets work and provide me with exactly what I need.

Thanks again.

Hopefully as I move along I'll be able to be just as helpful on this  
list.

Best Regards,

~Thomas


On Feb 17, 2008, at 11:38 PM, Andy wrote:

> Thomas,
>
> I'm new to Ruby (only a few days) but this is something I think I can
> actually help you with.  I had to do some searching and I came across
> this website ..
> http://pleac.sourceforge.net/pleac_ruby/fileaccess.html
>
> Search for 'Modifying a File in Place Without a Temporary File' and
> you'll find the code.  I'll paste it here though just to make it quick
> and easy ..
>
> File.open('itest', 'r+') do |f|   # open file for update
>    lines = f.readlines           # read into array of lines
>    lines.each do |it|            # modify lines
>        it.gsub!(/foo/, 'QQQ')
>    end
>    f.pos = 0                     # back to start
>    f.print lines                 # write out modified lines
>    f.truncate(f.pos)             # truncate to new length
> end                               # file is automatically closed
>
> r+ is the mode that allows you to read and write to the file.  I made
> a text file named itest with this for content ..
>
> foo foo
> bar bar
> foo foo
>
> I ran that code and the file got changed to ..
>
> QQQ QQQ
> bar bar
> QQQ QQQ
>
> That's what you're looking for isn't it?  I would suggest making a
> backup of the files just in case there is a problem.  If that isn't
> what you were looking for I apologize, reply back to this and I'll try
> again haha.
>
> -- 
> -Andy
> "I have a great faith in fools; self-confidence my friends call it." –
> Edgar Allen Poe
>
> On Feb 17, 2008 9:00 PM, Thomas Pierce <ruby@upgradeyourmind.com>  
> wrote:
>> Hello!
>>
>> I'm new to ruby and been reading this very active list for about a
>> couple of week.
>>
>> I have a project at work where I need to write a simple script to
>> scrub IP addresses from configuration files for classified networks  
>> we
>> work in sometimes. The goal is to cleanse configuration files
>> sometimes required for support of any specific network addressing
>> information. Here is what I've come up with so far. While this works
>> in IRB on the file object I create, I cannot figure out how to write
>> the changes back in place to the actual file itself back on the regex
>> I'm using:
>>
>>  config_file = File.open("config.txt")
>>         config_txt = config_file.read
>>         config_txt.gsub!(/\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}/,
>> "000.000.000.000")
>>
>> I do understand that the default action here is read-only. How to  
>> do I
>> parse with the regex on the current file and replace matching strings
>> without either appending to the file, overwriting the file, or
>> creating a new file?
>>
>> Thanks!
>>
>> ~Thomas
>>
>>
>