[Rd] cannot destroy connection (?) created by readLines in a tryCatch
Gábor Csárdi
csardi.gabor at gmail.com
Thu Dec 14 19:02:18 CET 2017
Consider this code. This is R 3.4.2, but based on a quick look at the
NEWS, this has not been fixed.
tryCatch(
readLines(tempfile(), warn = FALSE)[1],
error = function(e) NA,
warning = function(w) NA
)
rm(list=ls(all.names = TRUE))
gc()
showConnections(all = TRUE)
If you run it, you'll get a connection you cannot close(), i.e. the
last showConnections() call prints:
❯ showConnections(all = TRUE)
description
0 "stdin"
1 "stdout"
2 "stderr"
3 "/var/folders/59/0gkmw1yj2w7bf2dfc3jznv5w0000gn/T//Rtmpc7JqVS/filecc2044b2ccec"
class mode text isopen can read can write
0 "terminal" "r" "text" "opened" "yes" "no"
1 "terminal" "w" "text" "opened" "no" "yes"
2 "terminal" "w" "text" "opened" "no" "yes"
3 "file" "r" "text" "closed" "yes" "yes"
AFAICT, readLines should close the connection:
❯ readLines
function (con = stdin(), n = -1L, ok = TRUE, warn = TRUE, encoding = "unknown",
skipNul = FALSE)
{
if (is.character(con)) {
con <- file(con, "r")
on.exit(close(con))
}
.Internal(readLines(con, n, ok, warn, encoding, skipNul))
}
<environment: namespace:base>
so maybe this just a symptom of an on.exit() issue?
Or am I missing something and it is possible to close the connection?
Thanks,
Gabor
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