[Rd] Sys.readlink (on BSD vs Linux)

Sven Templer sven.templer at gmail.com
Mon Feb 29 11:59:41 CET 2016


sorry for not being clear enough.

My problem is represented with the following code, running on OSX:

mkdir ~/test
ln -s ~/test ~/testlink
touch ~/test/foo
Rscript -e 'Sys.readlink(c("~/test/foo", "~/testlink/foo")); normalizePath(c("~/test/foo","~/testlink/foo"))'

I expected `Sys.readlink` to show the same output as `normalizePath`.
Also, I think the readlink.h imported to R to be the same as from the system's `readlink` command, thus mimicking the command line difference.

Am I wrong with the latter? Anyway, the behaviour is irritating, thus the request to at least mention `normalizePath` in the Rd of `Sys.readlink`.


> On 29 Feb 2016, at 11:44, Mikko Korpela <mikko.korpela at aalto.fi> wrote:
> On 29.02.2016 10:34, Sven E. Templer wrote:
>> Hello together,
>> the function `Sys.readlink` uses the system's readlink command to resolve symlink paths. On OSX/BSD the command has a different meaning than on Linux [1].
>> There exists the tool 'realpath', which seems suitable for the task, at least applied at the command line level [2]. It is used in `normalizePath`.
>> I suggest (at least the latter) to
>> * use realpath instead readlink within Sys.readlink (do_readlink -> do_normalizepath)
>> * link to `normalizePath` in the Rd document, eventually mentioning the difference
>> Many thanks,
>> Sven
>> [1] see
>> https://www.freebsd.org/cgi/man.cgi?query=readlink
>> vs
>> http://linux.die.net/man/1/readlink
>> [2]
>> https://www.freebsd.org/cgi/man.cgi?query=realpath
>> http://linux.die.net/man/1/realpath
> What do you mean by "different meaning"? How are the command line tools
> [1] relevant when R is using the C function 'readlink'?
> http://pubs.opengroup.org/onlinepubs/9699919799/functions/readlink.html
> https://www.freebsd.org/cgi/man.cgi?query=readlink&sektion=2
> http://man7.org/linux/man-pages/man2/readlink.2.html
> -- 
> Mikko Korpela
> Aalto University School of Science
> Department of Computer Science

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