install.packages('xfun')'\n'on.exit() in a parent functionremotes::install_github()cat()FALSEoptions() and environment variablesgsub() on elements matched from grep()R CMD check on the reverse dependencies of a packagecurlstr() into a tree diagramrecord()system2() and mark its character output as UTF-8 if appropriateRscript()Rscript and R CMD