[R] Command line and R

[paul sorenson]

Angelo Secchi wrote:
> 
> On Wed, 09 Nov 2005 12:25:37 -0000 (GMT)
> (Ted Harding) <Ted.Harding at nessie.mcc.ac.uk> wrote:
> 
> 
>>On 09-Nov-05 Roger Bivand wrote:
>>
>>>On Wed, 9 Nov 2005, Angelo Secchi wrote:
>>>
>>>>Hi,
>>>>I wrote a small R script (delta.R) using commandArgs(). The script
>>>>works from the shell in usual way
>>>>
>>>>R --no-save arg1 < delta2.R
>>>>
>>>>Suppose arg1 is the output of another shell command (e.g. gawk,
>>>>sed ...). Is there a way to tell R to read arg1 from the
>>>>output of the previous command? Any other workaround?
>>>
>>>Use shell variables, possibly also Sys.getenv() within R as well as or 
>>>instead of commandArgs().
>>
>>If it's a fairly simple shell comand (and even if it isn't, though
>>it could get tricky for complicated ones) you can use the "backquote"
>>trick (called, in well-spoken circles, "command substitution"):
>>
>>  R --no-save `shellcmd` < delta2.R
>>
>>As in all shell command lines, wherever you have a command (including
>>arguments etc.) between backquotes, as exemplified by "`shellcmd`" above,
>>the output of the command (as sent to stdout) replaces "`shellcmd`" in
>>the command-line. This could be a lot of stuff (depending on what
>>"shellcmd" is), or just one value, or whatever.

... and this behaviour is OS (or at least command shell specific) for 
anyone trying this on Windows and wondering why it doesn't work.