[Rd] [R] shQuote and cat

[Vadim Organovich]

I feel like it now belongs to r-devel more than to r-help.

My output was garbled because I sent the original message as HTML, sorry about that.

Your output, "\"\\"a\\"\"", is what I get too. That is
 > cat(shQuote(shQuote(shQuote("a"))), '\n')
"\"\\"a\\"\""
, which I think should be "\"\\\"a\\\"\"".

Actually, the R's output, "\"\\"a\\"\"", is not even a valid string literal, that is
> x <- "\"\\"a\\"\""
fails.


Now, by cat() being the inverse of shQuote() I mean printing the same literal as it goes into shQuote, quotes included:
> cat(shQuote("a"), '\n')
"a"

whereas
> cat("a", '\n')
a  ## no quotes

If cat() is not the inverse of shQuote() in the above sense, what is?

Thanks,
Vadim
________________________________________
From: Duncan Murdoch [murdoch at stats.uwo.ca]
Sent: Wednesday, July 23, 2008 1:10 PM
To: Vadim Organovich
Cc: r-help at r-project.org
Subject: Re: [R] shQuote and cat

On 7/23/2008 12:20 PM, Vadim Organovich wrote:
> Dear R-users,
>
> It is my understanding that cat(shQuote(a.string)) should print the origintal a.string. Is this right?

No, cat(a.string) should print the original a.string.  shQuote(a.string)
adds quotes so that a.string can be used in the shell.

> I am not sure cat() correctly prints strings which are generated by triple-shQuote():
>
>> shQuote(shQuote("a"))
> [1] "\"\\\"a\\\"\""
>> cat(shQuote(shQuote(shQuote("a"))), '\n')
> "\"\\"a\\"\<file://\\"a\\"\>""

That's a very strange result.  I tried the obsolete version of R that
you're using, and I didn't see it. I get this:

 > cat(shQuote(shQuote(shQuote("a"))), '\n')
"\"\\"a\\"\""

Duncan Murdoch

> As you can see the latter string has fewer quoting '\' than the former.
> cat() of double shQuote works as expected:
>
>> shQuote("a")
> [1] "\"a\""
>> cat(shQuote(shQuote("a")), '\n')
> "\"a\""
>> version
>                _
> platform       i386-pc-mingw32
> arch           i386
> os             mingw32
> system         i386, mingw32
> status
> major          2
> minor          6.1
> year           2007
> month          11
> day            26
> svn rev        43537
> language       R
> version.string R version 2.6.1 (2007-11-26)
> Am I missing something?
>
> Thanks,
> Vadim
>
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