[R] Capturing info from system calls in Windows

[Duncan Murdoch]

On 26/01/2008 9:17 AM, Dennis Fisher wrote:
> Colleagues,
> 
> I am preparing scripts that will be used by others on both Windows and  
> Linux/OSX platforms.  The scripts call an existing Fortran  
> application.  The user may have any of a a variety of Fortran  
> compilers - my goal is to determine whether or not the test command  
> returns "no input files" or "command not found" (i.e., so that I can  
> confirm which Fortran they are using).
> 
> In OS X and Linux, I can do the following:
>>> TEST <- system("g77 2>&1", intern=TRUE)
>>> TEST
>> [1] "g77: no input files"
>>
>>> TEST <- system("f77 2>&1", intern=TRUE)
>>> TEST
>> [1] "sh: f77: command not found"
> I can then use grep to determine which of the two strings was returned.
> 
> In Windows:
>>> TEST <- system("g95 2>&1")
>> g95: 2>&1: Invalid argument
>>> TEST
>> [1] 0
>> attr(, "exec.status"):
>> [1] 0
>> attr(, "exit.status"):
>> [1] 0
>>> TEST <- system("g95")
>> g95: no input files
>>> TEST
>> [1] 0
>> attr(, "exec.status"):
>> [1] 0
>> attr(, "exit.status"):
>> [1] 0
> 
> As you can see, Windows replies "no input files"; however, that info  
> is not captured in TEST.  I presume that this is because standard  
> error is dealt with different in Windows compared to Unix-line  
> platforms.  Any thoughts on how to capture standard error in Windows?

See ?system.  You want intern=TRUE there, too.

 > system("gcc")
gcc.exe: no input files
 > system("gcc", intern=TRUE)
[1] "gcc.exe: no input files"


Duncan Murdoch

> 
> Dennis
> 
> 
> Dennis Fisher MD
> P < (The "P Less Than" Company)
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