[R] sprintf in system command

[Esam Tolba]

hi all
I am using r (2.15.2) in windows 7 32bit
I want to execute an external program from r console. the program is a
command line program which needs the following format to start
                                  C:/Users/.../dssp-2.0.4-win32.exe -i
data_1.txt -o data_1.dssp
I used the system command as:
                                  system
('C:/Users/.../dssp-2.0.4-win32.exe -i data.txt -o data.dssp')
it worked.
Now I want to use the program on a list of files, so for that I used a
for loop and sprintf
                                   for (i in 1:10) {
                                   system
('C:/Users/.../dssp-2.0.4-win32.exe -i sprintf("data_%s.txt",i) -o
sprintf("data_%s.dssp",i)')
but I received the following error
                    No such file
                    Warning message:
                    running command 'C:/Users/.../dssp-2.0.4-win32.exe
-i sprintf("data_%s.txt",i) -o sprintf("data_%s.dssp",i)' had status 1


SO, what is my mistake? and is there a way to update the input file
name based on  the for loop counter

Best Regards,