example(Sys.ps) fails on Alpine Linux

[bastistician]

On Alpine Linux, /bin/ps -> /bin/busybox provides fewer options than other implementations:

Usage: ps [-o COL1,COL2=HEADER] [-T]

Show list of processes

	-o COL1,COL2=HEADER	Select columns for display
	-T			Show threads

Thus, example(Sys.ps) fails for me:

> (.pid <- Sys.getpid()) ## process ID of current process
[1] 22939
> Sys.sizes(.pid)
/bin/ps: unrecognized option: p
Error in Sys.ps(process, c("rss", "vsz")) : 
  call returned less than two lines:
In addition: Warning message:
In system(cmd, intern = !usefile) :
  running command '/bin/ps w -p 22939 -o rss,vsz ' had status 1

Considering that there is already another report where this non-portable function fails its example (#7), the simplest "solution" (pacifying checks) would be to wrap the Sys.sizes() example in try(). (PS: also in robustbase/tests/MT-tst.R.)

[mmaechler]

Thank you; on the other hand, I won't no longer get notified about platforms where this fails ...

Indeed, the Alpine version of ps seems almost useless for things like this, as long as you can't specify the process id at all.

Could you leave the result of Sys.info() here?
If easily possible, I'd try to skip just "Alpine Linux" .. or I'd look if the ps file is a symlink to busybox and only then error out with something like
"ps command not powerful enough on this platform"

[bastistician]

Thanks. I wasn't sure how much effort you want to put into my report.

Throwing a more informative error message is nice but would not solve the check issue. You'd still have to wrap Sys.sizes() in try() or conditionalize its use. I see that Sys.ps() errors if a BSD is inferred from Sys.ps.cmd(), so the example is wrapped in try(). Alternatively, you could use \donttest (as intended for "code which might fail in circumstances that are hard to test for"): the examples would still run if checked --as-cran but not in regular checks.

Skipping on Alpine Linux would not be right as the 'procps-ng' implementation could be installed (it just isn't by default). It is hard to know which ps options are available without running it and checking the output and exit status. I guess you don't want to do this every time you use Sys.ps() and you may not want to add a configure step.