Capture both exit status and output from a system call in R

Question

I've been playing a bit with system() and system2() for fun, and it struck me that I can save either the output or the exit status in an object. A toy example:

X <- system("ping google.com",intern=TRUE)

gives me the output, whereas

X <- system2("ping", "google.com")

gives me the exit status (1 in this case, google doesn't take ping). If I want both the output and the exit status, I have to do 2 system calls, which seems a bit overkill. How can I get both with using only one system call?

EDIT : I'd like to have both in the console, if possible without going over a temporary file by using stdout="somefile.ext" in the system2 call and subsequently reading it in.

Answer 1

I am a bit confused by your description of system2, because it has stdout and stderr arguments. So it is able to return both exit status, stdout and stderr.

> out <- tryCatch(ex <- system2("ls","xx", stdout=TRUE, stderr=TRUE), warning=function(w){w})
> out
<simpleWarning: running command ''ls' xx 2>&1' had status 2>
> ex
[1] "ls: cannot access xx: No such file or directory"
> out <- tryCatch(ex <- system2("ls","-l", stdout=TRUE, stderr=TRUE), warning=function(w){w})
> out
 [listing snipped]                  
> ex
 [listing snipped]