getAbsolutePath: Gets the absolute pathname string
Description
  Gets the absolute pathname string.
Usage
"getAbsolutePath"(pathname, workDirectory=getwd(), expandTilde=FALSE, ...)
Arguments
pathname
A character string of the pathname to be converted into
   an absolute pathname. workDirectory
A character string of the current working directory. expandTilde
If TRUE, tilde (~) is expanded to the
   corresponding directory, otherwise not. Value
 Returns a character string of the absolute pathname.
Details
 This method will replace replicated slashes ('/') with a single one,
 except for the double forward slashes prefixing a Microsoft Windows UNC
 (Universal Naming Convention) pathname.