check if a program is installed

Question

I'm writing a function that uses pandoc in R through the command line. How can I use R to check if pandoc installed (I also assume it would have to be on the path which may be an issue for windows users)?

Answer 1

I don't have pandoc to install , but generally I test if a program is installed like this :

pandoc.installed <- system('pandoc -v')==0

For example to test if java is installed:

 java.installed <- system('java -version') ==0

java version "1.7.0_10"
Java(TM) SE Runtime Environment (build 1.7.0_10-b18)
Java HotSpot(TM) 64-Bit Server VM (build 23.6-b04, mixed mode)
> java.installed
[1] TRUE