[R] How to convert "c:\a\b" to "c:/a/b"

[Gabor Grothendieck]

Note that if you want to source it rather than than run it as a batch
job from the command line you will something like this.   The way
it works is that one puts the file name into comments that are
marked with tags and the script rereads itself as data picking out
the tagged lines and removing the tags from those lines.
script.name() returns the name of the script its running in and
my.stdin sets up a connection to the script as data after stripping out
all lines that do not match the tag and removing the tag from
those lines that do.  (This is a variation of some code that I previously
posted.)

# source the following from R

script.name <- function() 
 showConnections()[as.character(eval.parent(quote(file), n=3)), "description"]
my.stdin <- function( tag = "^#>", script.name. = script.name())
 textConnection( sub(tag, "", grep(tag,readLines(script.name.),value=TRUE)) )

x <- readLines( my.stdin() )
#>c:\a\b
cat(x, "\n")



On 6/29/05, Spencer Graves <spencer.graves at pdf.com> wrote:
> Thank You, Prof. Ripley!
> 
>          Both "test1.R" and "test2.R" worked for me just now, as did the
> following minor modification:
> 
> (x <- readLines(stdin(), n=1))
> D:\spencerg\dataPOWER\stats\Tukey\Boxplot_missing_Tukey2.txt
> 
>          Thanks again.
> 
>          spencer graves
> 
> Prof Brian Ripley wrote:
> > On Wed, 29 Jun 2005, David Duffy wrote:
> >
> >
> >>I couldn't resist adding a more literal answer
> >
> >
> > This can only work for escapes which are preserved.  The parser maps
> > \n to a character (LF) and the deparser maps it back to \n.
> > This happens to be true of \a \b \f \n \r \t \v \\ but no others.
> >
> > For example, \s is mapped to s, and there is no difference between \s and
> > s in the parsed input.
> >
> >
> >>unback <- function(x) {
> >> chars <- unlist(strsplit(deparse(x),""))
> >> chars <- chars[-c(1,length(chars))]
> >> paste(gsub("\\\\","/",chars),collapse="")
> >>}
> >>
> >>unback("\n")
> >
> >
> >>unback("\s")
> >
> > [1] "s"
> >
> > Spencer Graves keeps on insisting there is a better way, but all the
> > solutions are to avoid sending the string to the parser, and hence
> > avoiding having the string directly in an R script.  This is common in
> > shell scripts, which use 'here' documents to avoid 'quoting hell'.
> >
> > We can do that in R too. Here are two variants I have not seen in the
> > thread
> >
> > test1.R:
> > scan("", "", allowEscapes=FALSE, n=1, quiet=TRUE)
> > D:\spencerg\dataPOWER\stats\Tukey\Boxplot_missing_Tukey2.txt
> > catIx, "\n", sep="")
> >
> > R --slave --vanilla < test1.R
> > D:\spencerg\dataPOWER\stats\Tukey\Boxplot_missing_Tukey2.txt
> >
> > (This one does not allow quoted strings.)
> >
> > test2.R:
> > x <- readLines(stdin(), n=1)
> > "D:\spencerg\dataPOWER\stats\Tukey\Boxplot_missing_Tukey2.txt"
> > x <- gsub('^"(.*)"$', "\\1", x)
> > cat(x, "\n")
> >
> > R --slave --vanilla < test2.R
> > D:\spencerg\dataPOWER\stats\Tukey\Boxplot_missing_Tukey2.txt
> >
> > (This one allows surrounding quotes or not.)
> >
> 
> --
> Spencer Graves, PhD
> Senior Development Engineer
> PDF Solutions, Inc.
> 333 West San Carlos Street Suite 700
> San Jose, CA 95110, USA
> 
> spencer.graves at pdf.com
> www.pdf.com <http://www.pdf.com>
> Tel:  408-938-4420
> Fax: 408-280-7915
> 
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