It is precizely a shell command that I am trying to generate. To be specific let's try to have R 'output' the following shell command: 'echo "\"a\""'. This is is a valid command, at least in bash: bash-3.2$ echo "\"a\"" "a"
Now in R: > x <- 'echo "\"a\""' > cat(x, '\n') echo ""a"" > cat(shQuote(x), '\n') "echo \"\"a\"\"" Whichever way you do it it is not right. Again I think cat('echo "\"a\""') should be printing *echo "\"a\""* (asterics are not a part of the output) ________________________________________ From: Duncan Murdoch [EMAIL PROTECTED] Sent: Wednesday, July 23, 2008 2:38 PM To: Vadim Organovich Cc: r-devel@r-project.org Subject: Re: [Rd] [R] shQuote and cat 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 Note: This email is for the confidential use of the named addressee(s) only and may contain proprietary, confidential or privileged information. If you are not the intended recipient, you are hereby notified that any review, dissemination or copying of this email is strictly prohibited, and to please notify the sender immediately and destroy this email and any attachments. Email transmission cannot be guaranteed to be secure or error-free. Jump Trading, therefore, does not make any guarantees as to the completeness or accuracy of this email or any attachments. This email is for informational purposes only and does not constitute a recommendation, offer, request or solicitation of any kind to buy, sell, subscribe, redeem or perform any type of transaction of a financial product. ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel