R sink() message and output to same file - sanity check

Question

I'm using R's sink() function to capture errors, warnings, messages and console output into a single text file.

I'm wondering if simultaneously sinking both message and output types to a single open file is bad to do?

I capture all of the above into a single file, but I must open a file handle to allow both sink types to be captured. The following code illustrates using the file handle approach:

message_filename = 'script_messages.txt'
try(message_file <- file(message_filename, open="at")) # open file for appending in text mode
sink(message_file, type="message")
sink(message_file, type="output")

cat("\n\n")
message(format(Sys.time(), "%a %b %d %Y %X TZ(%z)"), appendLF = TRUE)
# next line produces messages since file doesn't exist
try(source("import_file.R"), silent = TRUE)

# Save and close writing errors, warnings, messages, and console output to a file
sink(type="output")
sink(type="message")
close(message_file)

If I don't open a file handle, then the sink 'output' type messages are the only ones captured in the text file.

The documentation on sink {base} has some key info in the first half of the Details section, but I'm not fluent enough to be sure I've implemented it properly.

Silkweed

Answer 1

I believe it's to do with the global option for warn. The default is warn=0 which means "warnings are stored until the top–level function returns". In other words, when you source("script.R"), R stores up the warnings and prints them once your script has finished, i.e. after you've run sink(type="output"); sink(type="message"); close(message_file).

To change this you can call options(warn=1) before you source your script, this will print warnings as they occur and will therefore be caught by your sink. This only needs to be run once per session.

Bruell