Re: Editing a text file and then replacing existing file

On Wed, Feb 2, 2011 at 5:31 PM, Jeremy Bopp <[e-mail]> wrote:
> On 2/2/2011 9:53 AM, Bob Hatch wrote:
>> I have a script that I use to find text in a file and then delete the
>> line(s) the text is on. That part works. What I have been unsuccessfully
>> trying to do is take the new text and overwrite the existing file that I
>> did the search and delete on. Here is my existing code that finds the
>> lines and deletes them:
>>
>> path=3D'c:\ruby192\my_projects\IIS_Logs\ex11012607.log'
>> search_text =3D %r{/memberinfo/downline/tree/can.asp}
>> search_text2 =3D %r{/memberinfo/downline/tree/disto.asp}
>> search_text3 =3D %r{/styles/default.css}
>> search_text4 =3D %r{/scripts/generalscript.js}
>> search_text5 =3D %r{/memberinfo/downline/tree/upl.asp}
>> search_text6 =3D %r{/scripts/wz_jsgraphics.js}
>> search_text7 =3D %r{/memberinfo/downline/tree/disfo2.asp}
>> search_text8 =3D %r{/styles/png.htc}
>> File.open(path, 'a+') do |file|
>> =A0 file.each_line do |line|
>> =A0 =A0 =A0 puts(line) unless line =3D~ search_text ||
>> =A0 puts(line) unless line =3D~ search_text2 ||
>> =A0 =A0 =A0 puts(line) unless line =3D~ search_text3 ||
>> =A0 =A0 =A0 puts(line) unless line =3D~ search_text4 ||
>> =A0 =A0 =A0 puts(line) unless line =3D~ search_text5 ||
>> =A0 =A0 =A0 puts(line) unless line =3D~ search_text6 ||
>> =A0 =A0 =A0 puts(line) unless line =3D~ search_text7 ||
>> =A0 =A0 =A0 puts(line) unless line =3D~ search_text8
>> =A0 =A0end
>> file.write(line)
>> file.close
>> end
>
> First of all, let's simplify this code by using a single regexp that
> will match all lines of interest. =A0This uses the x option for the regex=
p
> construction so that the format is a little more legible:
>
> search_text =3D %r{
> =A0/memberinfo/downline/tree/can.asp =A0 =A0|
> =A0/memberinfo/downline/tree/disto.asp =A0|
> =A0/styles/default.css =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0|
> =A0/scripts/generalscript.js =A0 =A0 =A0 =A0 =A0 =A0|
> =A0/memberinfo/downline/tree/upl.asp =A0 =A0|
> =A0/scripts/wz_jsgraphics.js =A0 =A0 =A0 =A0 =A0 =A0|
> =A0/memberinfo/downline/tree/disfo2.asp |
> =A0/styles/png.htc
> }x
>
> Beware that the x option will cause any unescaped whitespace in your
> regexp to be ignored, so you need to take care if you need to match a
> file path that has spaces in it.
>
> With this regexp you would be able to use a single puts(line) call.
> BTW, you should really try to avoid duplicated code like you have with
> your puts lines in general. =A0Alarm bells should go off in your head if
> you see that sort of thing. =A0More importantly though, you need to take =
a
> closer look at what you're doing there with the || operator. =A0That's no=
t
> exactly doing what you seem to intend. ;-)
>
> Now we get to the meat of your problem. =A0You can't write to the file
> from which you're reading without manually maintaining at least 2
> pointers into the file, one for your current read position and another
> for your write position. =A0It's *much* easier actually create a new file
> to hold the filtered data and then use that file to replace the original:
>
> File.open(source_path) do |infile|
> =A0File.open(temp_path, "w") do |outfile|
> =A0 =A0infile.each_line do |line|
> =A0 =A0 =A0outfile.write(line) unless line =3D~ search_text
> =A0 =A0end
> =A0end
> end
> File.rename(temp_path, source_path)

Just an additional perspective: for things like this it's probably
easier to use GNU fgrep:

$ fgrep -v -f search_texts input > output
$ mv input input~ && mv output input

Kind regards

robert

--=20
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/