How to write contents of help to a file from within R?

I'd like to be able to 开发者_StackOverflow中文版write the contents of a help file in R to a file from within R. The following works from the command-line:

• R --slave -e 'library(MASS); help(survey)' > survey.txt
  • This command writes the help file for the survey data file
  • --slave hides both the initial prompt and commands entered from the resulting output
  • -e '...' sends the command to R
  • > survey.txt writes the output of R to the file survey.txt

However, this does not seem to work:

library(MASS)
sink("survey.txt")
help(survey)
sink()

• How can I save the contents of a help file to a file from within R?

Looks like the two functions you would need are tools:::Rd2txt and utils:::.getHelpFile. This prints the help file to the console, but you may need to fiddle with the arguments to get it to write to a file in the way you want.

For example:

hs <- help(survey)
tools:::Rd2txt(utils:::.getHelpFile(as.character(hs)))

Since these functions aren't currently exported, I would not recommend you rely on them for any production code. It would be better to use them as a guide to create your own stable implementation.

While Joshua's instructions work perfectly, I stumbled upon another strategy for saving an R helpfile; So I thought I'd share it. It works on my computer (Ubuntu) where less is the R pager. It essentially just involves saving the file from within less.

• help(survey)
• Then follow these instructions to save less buffer to file
  • i.e., type g|$tee survey.txt
    • g goes to the top of the less buffer if you aren't already there
    • | pipes text between the range starting at current mark
    • and ending at $ which indicates the end of the buffer
    • to the shell command tee which allows standard out to be sent to a file