From: Jeremy McAnally <jeremymcanally@...>
Date: 2008-02-19T00:36:21+09:00
Subject: Re: Help with Writing Replacement Text to Files

Oh, right.  I forget that the "*+" modes do the primary letter ("w"
wipes the file for example) first, then "add on" the functionality of
the other (this must show how much I actually use those modes, eh?
:)).  Well, glad to help nonetheless.

--Jeremy

On Feb 18, 2008 9:35 AM, Thomas Pierce <ruby@upgradeyourmind.com> wrote:
> 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
> >>
> >>
> >
>
>
>



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