[R] Command line and R

[Angelo Secchi]

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.
> 
> Best wishes,
> Ted.

Thanks.
A.



> 
> 
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> Date: 09-Nov-05                                       Time: 12:25:32
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-- 
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 Angelo Secchi                     PGP Key ID:EA280337
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