How to run PowerShell command in R?

Question

For example, this PowerShell command returns the top 5 largest files in the directory:

gci -r |sort Length -desc |select fullname -f 5

Is it possible to run it in R and assign it to a variable?

I tried this:

system("gci -r|sort Length -desc|select fullname -f 5")
Warning message:
running command 'gci -r|sort Length -desc|select fullname -f 5' had status 127 

Shouldn't I use system() here?

Answer 1

You'll probably need to run it as (assuming PowerShell is in your path):

system("powershell -command \"gci -r|sort Length -desc|select fullname -f 5\"")

or, if you're not keen on escaping " with \".

system('powershell -command "gci -r|sort Length -desc|select fullname -f 5"')

I'm also assuming that's how R escapes and embeds quotes in strings (from my cursory googling about string handling in R).

If you wish to capture the output to a variable (specifically, a character vector) you need to use the intern = TRUE argument:

res <- system('powershell -command "gci -r|sort Length -desc|select fullname -f 5"', intern=TRUE)

For more information see:

http://stat.ethz.ch/R-manual/R-patched/library/base/html/system.html

In particular:

If intern = TRUE, a character vector giving the output of the command, one line per character string.

and

If intern = FALSE, the return value is an error code (0 for success),