On 15/03/2013 10:40, Jannis wrote:
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
If reading from stdin, it does (like any other interpreter): however
stdin is buffered if re-directed, so the input script is read in blocks
from a file (the size of the block depending on the OS).
individual commands. No idea though what happens if i would start the
script via source inside R itself.
R is Open Source, and you can read the code of source(). It really
isn't hard to see that it parses the whole file, then executes the
parsed expressions one at a time.
Thanks again for your suggestions
Jannis
On 14.03.2013 22:47, Rolf Turner wrote:
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
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