How to fix error “closing unused connection”

问题

To read in the first 5 columns of Test.csv I may go:

x <- matrix(scan(pipe(paste0("cut -f1,2,3,4,5 -d, ","/home/test/Test.csv")),skip=1,sep=","),ncol=5)

Then if I read it using a normal method:

y <- read.csv("/home/test/Test.csv")

I get the error message:

Warning message:
closing unused connection 3 (cut -f1,2,3,4,5 -d, /home/test/Test.csv)

Is this error message a problem, and if so how do I remedy it?

回答1:

I cannot replicate the warning on my system. However, you could try closing the connection explicitly:

con <- pipe(paste0("cut -f1,2,3,4,5 -d, ","/home/test/Test.csv"))
x <- matrix(scan(con,skip=1,sep=","),ncol=5)
close(con)

来源：https://stackoverflow.com/questions/19751555/how-to-fix-error-closing-unused-connection