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Generates a closure that writes binary (raw) data to a file.
file_writer(path, append = FALSE)Function with signature writer(data = raw(), close = FALSE)
file name or path on disk
open file in append mode
The writer function automatically opens the file on the first write and closes when
it goes out of scope, or explicitly by setting close = TRUE. This can be used
for the data callback in multi_add() or curl_fetch_multi() such
that we only keep open file handles for active downloads. This prevents running out
of file descriptors when performing thousands of concurrent requests.
# Doesn't open yet
tmp <- tempfile()
writer <- file_writer(tmp)
# Now it opens
writer(charToRaw("Hello!\n"))
writer(charToRaw("How are you?\n"))
# Close it!
writer(charToRaw("All done!\n"), close = TRUE)
# Check it worked
readLines(tmp)
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