[R] regular expression

[Laurent Rhelp]

Dear R-List,

     I have a great many files in a directory and I would like to 
replace in every file the character " by the character ' and in the same 
time, I have to change ' by '' (i.e. the character ' twice and not the 
unique character ") when the character ' is embodied in "....."
  So, "....." becomes '.....' and ".....'......" becomes '.....''......'
Certainly, regular expression could help me but I am not able to use it.

How can I do that with R ?

Thank you very much