[R] escape characters in shell commands

[Gabor Grothendieck]

On Tue, May 24, 2011 at 1:40 PM, James Rome <jamesrome at gmail.com> wrote:
> On a Windows platform I am trying to count the number of lines in a file.
> In a DOS window, the following works:
> C:\Users\jar>findstr /R /N "^" D:\my_dir\my_file | find /C ":"
> 5317
> (it works with double \\ also)
>
> But in R, I need to make this string up with the file name I get from
> file.choose():
> filename = file.choose()
> #get the number of lines in the file
> # first make a command string with the filename in it
> cmd = paste('findstr /R /N "^" ', filename, ' | find /C ":"', sep=""')
> nrec = as.numeric(shell(cmd))
>
> But R puts in escape characters for the ":
>> cmd
> [1] "findstr /R /N \"^\" D:\\my_dir\\my_file | find /C \":\""
>
> and shell(cmd) does not work properly. And
>> nrec=shell('findstr /R /N "^"D:\\my_dir\\my_file | find /C ":"')
>> nrec
> [1] 0
> does not work either.

Just a guess but note that Rtools has a find.exe so if you have Rtools
on your path before C:\Windows\System32 then the above won't work. You
can check it via:

shell("where find.exe")

If that is the problem then workarounds include using the full path to
find, using wc (which is included in Rtools) or doing it entirely in
R.




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