On 7/23/2008 2:53 PM, Vadim Organovich wrote:
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.
It's not intended to be a string literal in R, it's intended to be input
to the Windows CMD shell. If you want a string literal in R, don't use
cat(). cat() shows you the naked contents of the string without any
quoting to make it a valid string literal.
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?
On Unix-like systems I think asking the shell to echo the output, i.e.
system(paste("echo", shQuote(input)), intern=TRUE)
is intended to reproduce the input. However, the Windows CMD shell is
different. I don't know how to strip quotes off a string in it, e.g. I see
C:\WINDOWS\system32 echo "a"
"a"
Nevertheless, the quotes *are* necessary when passing filenames to
commands, and they'll typically be stripped off when doing that, e.g.
echo hi >"a"
will create a file named a, not named "a", and
echo hi >"a b"
will create a file with a space in the name.
Duncan Murdoch
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