On 8/24/2007 10:33 AM, Dirk Eddelbuettel wrote:
> On Fri, Aug 24, 2007 at 08:32:00AM -0400, Duncan Murdoch wrote:
>> On 8/24/2007 6:58 AM, Ronaldo Reis Junior wrote:
>> > Hi,
>> >
>> > It is possible to use a shell command inside a R script?
>> >
>> > I'm write a R script and I like to put somes shell commands inside to R.
>> > Somethink like: convert fig01.png fig01.xpm or sed ..., etc.
>>
>> The details and available functions depend on the platform, but you want
>> to look at ?system, ?shell, and/or ?shell.exec. (These all exist in
>> Windows; on Unix-alikes, you probably won't have the latter two.)
>
> Don't forget pipes.
>
> R's ability to consistently work on connections that may be local
> files, remotes files, program output, ... is a true treasure (and
> thanks and credits to, I believe, Brian Ripley to make it so).
>
> Eg you can do this
>
> OD <- read.table(pipe("links -dump http://cran.r-project.org/src/contrib/ |
> awk '/tar.gz/ {print $3, $4}'"), header=FALSE, col.names=c("file", "date"))
>
> to get files and dates of files on CRAN.
>
> As I recall, this also works on that other operating system, provided
> you do all the legwork of installing other tools, setting PATHs etc
> to provide what works out of the box on the supposedly unfriendlier OS.
The pipe command you list doesn't work in Windows. I'd guess this is
because the pipe syntax "|" within the command is unsupported: it tries
to execute "links", with the rest of the line passed as arguments. But
I haven't traced through to check on this.
Duncan Murdoch
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