[Rd] Dialect for shell scripts

[Rodrigo Tobar]

Dear all,

During a recent package submission, we were highlighted that some lines 
in our configure script didn't follow the correct syntax. The lines 
looked like this:

x=$(($y/10))

We were indicated at the time that this is because the statement does 
not use Bourne shell syntax, which is absolutely true, and also that the 
manual warns about this, which is true again. So far everything is clear.

However, what confuses me is that even when the manual says that "you 
can include an executable (Bourne) shell script configure in your 
package" [1], the associated footnote says something slightly different: 
"The script should only assume a POSIX-compliant /bin/sh" [2]. The 
footnote goes even further, and links to the POSIX specification of the 
Shell Command Language [3] (as published by The Open Group), which 
explicitly includes arithmetic expressions like the one above in its 
syntax [4].

My question then is: what exact dialect should be considered? Given that 
the statement above does not work in the Bourne shell, I conclude that 
the Bourne shell is not POSIX-compliant. That in turn would make the 
manual ambiguous as to the precise dialect that should be used by our 
configure scripts, and either the shells used by R should be changed to 
be POSIX-compliants, or the manual edited to be more precise regarding .

Many thanks.

Rodrigo

[1] 
https://cran.r-project.org/doc/manuals/r-release/R-exts.html#Configure-and-cleanup
[2] https://cran.r-project.org/doc/manuals/r-release/R-exts.html#FOOT25
[3] http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html
[4] 
http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_06_04