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 

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

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

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')

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"

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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