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comp.lang.ruby

How to use regexp to replace character with backslash plus this character

Maciej Pilichowski

11/18/2006 5:31:00 PM

Hello,

1.8.5.

I want to 'correct' filenames for unix shell so I want to preceed
any let's say & with backslash. Here is code translated from my
original script in Perl -- end of the function

return filename.gsub(/([\;\!\&\%\$\' ])/,'\\\1')

However it doesn't do anything good. If I put space in the middle
\\ \1

the replacament is correctly recognized. But I don't want to use
space in the middle. What's wrong here?

have a nice day
bye
--
Maciej "MACiAS" Pilichowski http://bantu.fm.i...
6 Answers

Paul Lutus

11/18/2006 6:03:00 PM

0

Maciej Pilichowski wrote:

> Hello,
>
> 1.8.5.
>
> I want to 'correct' filenames for unix shell so I want to preceed
> any let's say & with backslash. Here is code translated from my
> original script in Perl -- end of the function
>
> return filename.gsub(/([\;\!\&\%\$\' ])/,'\\\1')
>
> However it doesn't do anything good. If I put space in the middle
> \\ \1
>
> the replacament is correctly recognized. But I don't want to use
> space in the middle. What's wrong here?

-------------------------------
#!/usr/bin/ruby -w

data = ";!&%$"

data.gsub!(%r{([;!&%$' ])},'\\\\\1')

puts data
-------------------------------

Output:

\;\!\&\%\$

--
Paul Lutus
http://www.ara...

Maciej Pilichowski

11/18/2006 6:31:00 PM

0

On Sat, 18 Nov 2006 10:02:59 -0800, Paul Lutus <nospam@nosite.zzz>
wrote:

>data.gsub!(%r{([;!&%$' ])},'\\\\\1')

Thank you. But what is the interpretation of 5! backshlashes. First
two to achieve one textual backslash -- the last one, to get the
on-fly variable. And the rest two?

have a nice day
bye
--
Maciej "MACiAS" Pilichowski http://bantu.fm.i...

Gavin Kistner

11/18/2006 6:48:00 PM

0

Maciej Pilichowski wrote:
> Thank you. But what is the interpretation of 5! backshlashes. First
> two to achieve one textual backslash -- the last one, to get the
> on-fly variable. And the rest two?

Please search the mailing list archive - this question comes up at
least once a month.

Try this:
http://groups.google.com/group/comp.lang.ruby/search?group=comp.lang.ruby&q=backslash&...

Maciej Pilichowski

11/18/2006 7:15:00 PM

0

On 18 Nov 2006 10:47:44 -0800, "Phrogz" <gavin@refinery.com> wrote:

>Please search the mailing list archive - this question comes up at
>least once a month.

Thank you, but as you can see -- google -- not in that context -- so
often. I found 'answer' at RubyCentral, but I am still not convinced
it works properly. Why
\\ \1
is ok, but
\\\1
not? If there is some kind of two-pass parsing -- as RubyCentral
explains
\\ \1
should be converted to
\1
or even
1
but it is not.

It looks like some too greedy substitution/parsing algorithm -- I mean
at first the two first backshlashes are grouped together, then the
second and the third.

have a nice day
bye
--
Maciej "MACiAS" Pilichowski http://bantu.fm.i...

William James

11/19/2006 2:24:00 AM

0

Paul Lutus wrote:
> Maciej Pilichowski wrote:
>
> > Hello,
> >
> > 1.8.5.
> >
> > I want to 'correct' filenames for unix shell so I want to preceed
> > any let's say & with backslash. Here is code translated from my
> > original script in Perl -- end of the function
> >
> > return filename.gsub(/([\;\!\&\%\$\' ])/,'\\\1')
> >
> > However it doesn't do anything good. If I put space in the middle
> > \\ \1
> >
> > the replacament is correctly recognized. But I don't want to use
> > space in the middle. What's wrong here?
>
> -------------------------------
> #!/usr/bin/ruby -w
>
> data = ";!&%$"
>
> data.gsub!(%r{([;!&%$' ])},'\\\\\1')
>
> puts data
> -------------------------------
>
> Output:
>
> \;\!\&\%\$

irb(main):055:0> puts ";!&%$".gsub( /[;!&%$]/, '\\\\\&' )
\;\!\&\%\$

irb(main):008:0> puts ";!&%$".gsub( /[;!&%$]/ ){ "\\" + $& }
\;\!\&\%\$

irb(main):009:0> puts ";!&%$".gsub( /[;!&%$]/ ){ "\\#{ $& }" }
\;\!\&\%\$

irb(main):011:0> puts ";!&%$".gsub( /([;!&%$])/ ){ "\\#{ $1 }" }
\;\!\&\%\$

Paul Lutus

11/19/2006 3:17:00 AM

0

William James wrote:

/ ...

> irb(main):055:0> puts ";!&%$".gsub( /[;!&%$]/, '\\\\\&' )
> \;\!\&\%\$
>
> irb(main):008:0> puts ";!&%$".gsub( /[;!&%$]/ ){ "\\" + $& }
> \;\!\&\%\$
>
> irb(main):009:0> puts ";!&%$".gsub( /[;!&%$]/ ){ "\\#{ $& }" }
> \;\!\&\%\$
>
> irb(main):011:0> puts ";!&%$".gsub( /([;!&%$])/ ){ "\\#{ $1 }" }
> \;\!\&\%\$

Yes, except that I hate using those Perlish globals. Just a personal thing.

--
Paul Lutus
http://www.ara...