man/examples/ex_grassHelp.r

In fasterRaster: Faster Raster and Spatial Vector Processing Using 'GRASS GIS'

if (grassStarted() & interactive()) {

# Open help pages for `r.mapcalc` and `r.sun`:
grassHelp("r.mapcalc")
grassHelp("r.sun")

# GRASS table of contents:
grassHelp("toc")

# Index page:
grassHelp("index")

}