R help - Sep 2011 - Open file for reading and writing with APPEND

Hi,

I want to keep a running file of some statistics generated by a running process.
Occasionally the process will be restarted.

On  restart, I'd like to read the last line of the log file to set some
variables to their last state, and then continue to append values to that same
file.

I can't seem to get the appending part to work.  I can read values form the
file, but then upon the first write, the file is overwritten with the new
values, so I lose my entire history.

Any ideas?

Here is what I'm using:


============================outfile <- file("logfile.csv",
open="r")
x <- readLines(outfile)
lastLine <- x[length(x)]
a <- as.numeric( strsplit(lastLine, " +")[[1]][1] )
b <- as.numeric( strsplit(lastLine, " +")[[1]][2] )
c <- as.numeric( strsplit(lastLine, " +")[[1]][3] )
close(outfile)

outfile <- file("logfile.csv", open="w")


while(1){
	# do a bunch of stuff
	cat(a, b, c, sep=",", "\n",  file=outfile, append=TRUE)
	
}

========================

--
Noah Silverman
UCLA Department of Statistics
8117 Math Sciences Building #8208
Los Angeles, CA 90095

See details on *argument* 'open' for file(), cf. help("file").

/Henrik

On Wed, Sep 14, 2011 at 12:38 PM, Noah Silverman <noahsilverman at
ucla.edu> wrote:
> Hi,
>
> I want to keep a running file of some statistics generated by a running
process. ?Occasionally the process will be restarted.
>
> On ?restart, I'd like to read the last line of the log file to set some
variables to their last state, and then continue to append values to that same
file.
>
> I can't seem to get the appending part to work. ?I can read values form
the file, but then upon the first write, the file is overwritten with the new
values, so I lose my entire history.
>
> Any ideas?
>
> Here is what I'm using:
>
>
> ============================> outfile <-
file("logfile.csv", open="r")
> x <- readLines(outfile)
> lastLine <- x[length(x)]
> a <- as.numeric( strsplit(lastLine, " +")[[1]][1] )
> b <- as.numeric( strsplit(lastLine, " +")[[1]][2] )
> c <- as.numeric( strsplit(lastLine, " +")[[1]][3] )
> close(outfile)
>
> outfile <- file("logfile.csv", open="w")
>
>
> while(1){
> ? ? ? ?# do a bunch of stuff
> ? ? ? ?cat(a, b, c, sep=",", "\n", ?file=outfile,
append=TRUE)
>
> }
>
> ========================>
>
> --
> Noah Silverman
> UCLA Department of Statistics
> 8117 Math Sciences Building #8208
> Los Angeles, CA 90095
>
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