does R read commands from scripts instantanously or seuqently during processing

Dear all,

thanks, Rolf and Jeff, for your replies. The command below runs under 
Suse Linux. I guess, hoewever, the phenomena I observed would heappen 
under other oprating systems as well. The reason why I asked was that R 
produced some error messages that did not really point me to the 
direction of the edited script file. These errors were usually something 
like:

Error: unexpected symbol in "cess finished."

The line in the script which caused this error is:

print(paste(as.character(Sys.time()), ': Process finished.', sep=''))

This line contains valid R code and would normally not produce an error. 
Some testing showed that the error above only happens when I edit the 
code of the script while the script is run. So R probably reads in a 
script submitted that way seuqently directly while executing the 
individual commands. No idea though what happens if i would start the 
script via source inside R itself.


Thanks again for your suggestions
Jannis

On 03/15/2013 05:13 AM, Jannis wrote:

Dear R community,


when I source a script into R via:


R --slave < scriptname.R


is the whole script file read at once during startup or is each
indivdual line of code read seqnetially during the execution (i.e.
directly before r processes the respective command)? In other words,
can I savely edit the  scriptname.R file even when an active R process
still runs the command above?

Experiment.  Build a toy script with a loop that never terminates. Set
it going.  Edit the script and change the code so that the loop terminates.
See what happens.

[It seems to me that nothing happens, so that you *can* "safely" edit
the script while
the process runs.  But further experimentation would be advisable.]

     cheers,

         Rolf Turner