[R] R CMD BATCH character limit?

[Prof Brian Ripley]

On Tue, 1 Feb 2005, Hsiu-Khuern Tang wrote:

> Is there a limit on the number of characters in an invocation like
>
> R CMD BATCH --opt1=val1 --opt2=val2 ... --save-to=C:\very\long\string ..\R\script.R
>
> ?

Yes, but that is not a valid invocation of R.

> I am running R 2.0.1 on Windows XP, and when running a long BATCH
> command (about 400--500 characters) the last option gets mangled, as can

There is a Windows limit on the length of command lines, and I believe you 
have hit it.  It looks like R.exe/Rcmd.exe were written assuming it is 
MAX_PATH, hence about 260, which it used to be in Win95.

You could use

rterm --args --opt1=val1 --opt2=val2 ... --save-to=C:\very\long\string < foo > bar

instead: BATCH is just a convenient shorthand (and see the rw-FAQ for the 
details).

Shells also have limits, so check this for the one you used.

> be seen from a warning in script.Rout that looks like this:
>
> WARNING: unknown option
> +--save-to=C:\very\long\str..\R\script.Rout
>
> Note that "string" is truncated to "str" _and_ concatenated with the
> implicit batch output file "..\R\script.Rout".  (The "unknown option"
> warning is expected; I am just using commandArgs() within the script to
> pick out the arguments.)
>
> I have tried specifying --args before the options, with the same result,
> except that the truncation appears earlier.

--args would be needed for this to make any sense.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595