Sys.readlink (on BSD vs Linux)

On Feb 29, 2016, at 5:59 AM, Sven Templer <sven.templer at gmail.com> wrote:

Hello,

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`.

Best,
Sven

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