Quoting "Heuvel, E.G. van den (Guido)" <g.vandenheu...@cbs.nl>:
-----Oorspronkelijk bericht-----
Van: Enrico Schumann <e...@enricoschumann.net>
Verzonden: woensdag 25 juni 2025 16:44
Aan: Heuvel, E.G. van den (Guido) <g.vandenheu...@cbs.nl>
CC: 'r-help@R-project.org' <r-help@r-project.org>
Onderwerp: Re: [R] Potential bug in readLines when reading empty lines
Quoting "Heuvel, E.G. van den (Guido) via R-help" <r-help@r-project.org>:
Hi all,
I encountered some weird behaviour with readLines() recently, and I >
am wondering if this might be a bug, or, if it is not, how to > resolve
it. The issue is as follows:
If I have a text file where a line ends with just a carriage return >
(\r,
CR) while the next line is empty and ends in a carriage return > /
linefeed (\r\n, CR LF), then the empty line is skipped when > reading
the file with readLines. The following code contains a test > case:
---
print(R.version)
# platform x86_64-w64-mingw32
# arch x86_64
# os mingw32
# crt ucrt
# system x86_64, mingw32
# status
# major 4
# minor 4.0
# year 2024
# month 04
# day 24
# svn rev 86474
# language R
# version.string R version 4.4.0 (2024-04-24 ucrt)
# nickname Puppy Cup
txt_original <- paste0("Line 1\r", "\r\n", "Line 3\r\n")
# Write txt_original as binary to avoid unwanted conversion of end >
of line markers writeBin(charToRaw(txt_original), "test.txt")
txt_actual <- readLines("test.txt")
print(txt_actual)
# [1] "Line 1" "Line 3"
---
I included the output of this script on my machine in the comments. >
I would expect txt_actual to be equal to c("Line 1", "", "Line 3"), >
but the empty line is skipped.
Is this a bug? And if not, how should I read test.txt in such a way >
that the empty 2nd line is left intact?
Best regards,
Guido van den Heuvel
Statistics Netherlands
What would be your "rule" for identifying lines? From your desired
output, it seems \r should be end-of-line, and \n is to be ignored.
Then you could do something like that:
raw <- readChar("test.txt", 1000)
raw <- gsub("\n", "", raw)
strsplit(raw, "\r")[[1]]
## [1] "Line 1" "" "Line 3"
But it requires you to specify the number of characters to read (or
write a loop).
My preferred rule would be the current documentation of the
readLines function. Specifically, the line "Whatever mode the
connection is opened in, any of LF, CRLF or CR will be accepted as
the EOL marker for a line."
As a workaround, you could do something like this:
raw <- readChar("test.txt", 1000)
raw <- gsub("\r\n", "\n", raw)
raw <- gsub("\r", "\n", raw)
strsplit(raw, "\n")[[1]]
## [1] "Line 1" "" "Line 3"
Of course, if the true file was created with
txt <- paste0("Line 1\r", "\n", "\r\n", "Line 4\r")
then "Line 1\r" and "\n" will be merged into one line.
--
Enrico Schumann
Lucerne, Switzerland
http://enricoschumann.net
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